foo.cc: In function 'int main()':
foo.cc:6:9: error: no match for 'operator>>' (operand types are 'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} and 'char')
    6 |   cin>>a>>','>>b;
      |   ~~~~~~^~~~~
      |      |    |
      |      |    char
      |      std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}
In file included from iostream:40:
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:120:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__istream_type& (*)(__istream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  120 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |       ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:120:7: note:   conversion of argument 1 would be ill-formed:
foo.cc:6:11: error: invalid conversion from 'char' to 'std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&)' {aka 'std::basic_istream<char>& (*)(std::basic_istream<char>&)'} [-fpermissive]
    6 |   cin>>a>>','>>b;
      |           ^~~
      |           |
      |           char
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:124:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__ios_type& (*)(__ios_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>; __ios_type = std::basic_ios<char>]' (near match)
  124 |       operator>>(__ios_type& (*__pf)(__ios_type&))
      |       ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:124:7: note:   conversion of argument 1 would be ill-formed:
foo.cc:6:11: error: invalid conversion from 'char' to 'std::basic_istream<char>::__ios_type& (*)(std::basic_istream<char>::__ios_type&)' {aka 'std::basic_ios<char>& (*)(std::basic_ios<char>&)'} [-fpermissive]
    6 |   cin>>a>>','>>b;
      |           ^~~
      |           |
      |           char
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:131:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::ios_base& (*)(std::ios_base&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  131 |       operator>>(ios_base& (*__pf)(ios_base&))
      |       ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:131:7: note:   conversion of argument 1 would be ill-formed:
foo.cc:6:11: error: invalid conversion from 'char' to 'std::ios_base& (*)(std::ios_base&)' [-fpermissive]
    6 |   cin>>a>>','>>b;
      |           ^~~
      |           |
      |           char
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:168:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  168 |       operator>>(bool& __n)
      |       ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:168:7: note:   conversion of argument 1 would be ill-formed:
foo.cc:6:11: error: cannot bind non-const lvalue reference of type 'bool&' to a value of type 'char'
    6 |   cin>>a>>','>>b;
      |           ^~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:172:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  172 |       operator>>(short& __n);
      |       ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:172:7: note:   conversion of argument 1 would be ill-formed:
foo.cc:6:11: error: cannot bind non-const lvalue reference of type 'short int&' to a value of type 'char'
    6 |   cin>>a>>','>>b;
      |           ^~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:175:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  175 |       operator>>(unsigned short& __n)
      |       ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:175:7: note:   conversion of argument 1 would be ill-formed:
foo.cc:6:11: error: cannot bind non-const lvalue reference of type 'short unsigned int&' to a value of type 'char'
    6 |   cin>>a>>','>>b;
      |           ^~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:179:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  179 |       operator>>(int& __n);
      |       ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:179:7: note:   conversion of argument 1 would be ill-formed:
foo.cc:6:11: error: cannot bind non-const lvalue reference of type 'int&' to a value of type 'char'
    6 |   cin>>a>>','>>b;
      |           ^~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:182:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  182 |       operator>>(unsigned int& __n)
      |       ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:182:7: note:   conversion of argument 1 would be ill-formed:
foo.cc:6:11: error: cannot bind non-const lvalue reference of type 'unsigned int&' to a value of type 'char'
    6 |   cin>>a>>','>>b;
      |           ^~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:186:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  186 |       operator>>(long& __n)
      |       ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:186:7: note:   conversion of argument 1 would be ill-formed:
foo.cc:6:11: error: cannot bind non-const lvalue reference of type 'long int&' to a value of type 'char'
    6 |   cin>>a>>','>>b;
      |           ^~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:190:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  190 |       operator>>(unsigned long& __n)
      |       ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:190:7: note:   conversion of argument 1 would be ill-formed:
foo.cc:6:11: error: cannot bind non-const lvalue reference of type 'long unsigned int&' to a value of type 'char'
    6 |   cin>>a>>','>>b;
      |           ^~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:195:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  195 |       operator>>(long long& __n)
      |       ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:195:7: note:   conversion of argument 1 would be ill-formed:
foo.cc:6:11: error: cannot bind non-const lvalue reference of type 'long long int&' to a value of type 'char'
    6 |   cin>>a>>','>>b;
      |           ^~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:199:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  199 |       operator>>(unsigned long long& __n)
      |       ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:199:7: note:   conversion of argument 1 would be ill-formed:
foo.cc:6:11: error: cannot bind non-const lvalue reference of type 'long long unsigned int&' to a value of type 'char'
    6 |   cin>>a>>','>>b;
      |           ^~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:214:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(float&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  214 |       operator>>(float& __f)
      |       ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:214:7: note:   conversion of argument 1 would be ill-formed:
foo.cc:6:11: error: cannot bind non-const lvalue reference of type 'float&' to a value of type 'char'
    6 |   cin>>a>>','>>b;
      |           ^~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:218:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  218 |       operator>>(double& __f)
      |       ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:218:7: note:   conversion of argument 1 would be ill-formed:
foo.cc:6:11: error: cannot bind non-const lvalue reference of type 'double&' to a value of type 'char'
    6 |   cin>>a>>','>>b;
      |           ^~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:222:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  222 |       operator>>(long double& __f)
      |       ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:222:7: note:   conversion of argument 1 would be ill-formed:
foo.cc:6:11: error: cannot bind non-const lvalue reference of type 'long double&' to a value of type 'char'
    6 |   cin>>a>>','>>b;
      |           ^~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:235:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  235 |       operator>>(void*& __p)
      |       ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:235:7: note:   conversion of argument 1 would be ill-formed:
foo.cc:6:11: error: invalid conversion from 'char' to 'void*' [-fpermissive]
    6 |   cin>>a>>','>>b;
      |           ^~~
      |           |
      |           char
foo.cc:6:11: error: cannot bind rvalue '(void*)44' to 'void*&'
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:259:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(__streambuf_type*) [with _CharT = char; _Traits = std::char_traits<char>; __streambuf_type = std::basic_streambuf<char>]' (near match)
  259 |       operator>>(__streambuf_type* __sb);
      |       ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:259:7: note:   conversion of argument 1 would be ill-formed:
foo.cc:6:11: error: invalid conversion from 'char' to 'std::basic_istream<char>::__streambuf_type*' {aka 'std::basic_streambuf<char>*'} [-fpermissive]
    6 |   cin>>a>>','>>b;
      |           ^~~
      |           |
      |           char
foo.cc:6:9: note: candidate: 'operator>>(int, int)' (built-in)
    6 |   cin>>a>>','>>b;
      |   ~~~~~~^~~~~
foo.cc:6:9: note:   no known conversion for argument 1 from 'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} to 'int'
In file included from /nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/string:54,
                 from /nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/bits/locale_classes.h:40,
                 from /nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/bits/ios_base.h:41,
                 from /nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/ios:42,
                 from /nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/ostream:38,
                 from iostream:39:
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/bits/basic_string.tcc:940:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::basic_istream<_CharT, _Traits>& std::operator>>(basic_istream<_CharT, _Traits>&, __cxx11::basic_string<_CharT, _Traits, _Alloc>&)'
  940 |     operator>>(basic_istream<_CharT, _Traits>& __in,
      |     ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/bits/basic_string.tcc:940:5: note:   template argument deduction/substitution failed:
foo.cc:6:11: note:   mismatched types 'std::__cxx11::basic_string<_CharT, _Traits, _Alloc>' and 'char'
    6 |   cin>>a>>','>>b;
      |           ^~~
In file included from /nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:1016:
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/bits/istream.tcc:975:5: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::operator>>(basic_istream<_CharT, _Traits>&, _CharT&) [with _CharT = char; _Traits = char_traits<char>]' (near match)
  975 |     operator>>(basic_istream<_CharT, _Traits>& __in, _CharT& __c)
      |     ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/bits/istream.tcc:975:5: note:   conversion of argument 2 would be ill-formed:
foo.cc:6:11: error: cannot bind non-const lvalue reference of type 'char&' to an rvalue of type 'char'
    6 |   cin>>a>>','>>b;
      |           ^~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:756:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, unsigned char&)'
  756 |     operator>>(basic_istream<char, _Traits>& __in, unsigned char& __c)
      |     ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:756:5: note:   template argument deduction/substitution failed:
foo.cc:6:11: note:   cannot convert '','' (type 'char') to type 'unsigned char&'
    6 |   cin>>a>>','>>b;
      |           ^~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:761:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, signed char&)'
  761 |     operator>>(basic_istream<char, _Traits>& __in, signed char& __c)
      |     ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:761:5: note:   template argument deduction/substitution failed:
foo.cc:6:11: note:   cannot convert '','' (type 'char') to type 'signed char&'
    6 |   cin>>a>>','>>b;
      |           ^~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:803:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(basic_istream<_CharT, _Traits>&, _CharT*)'
  803 |     operator>>(basic_istream<_CharT, _Traits>& __in, _CharT* __s)
      |     ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:803:5: note:   template argument deduction/substitution failed:
foo.cc:6:11: note:   mismatched types '_CharT*' and 'char'
    6 |   cin>>a>>','>>b;
      |           ^~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:846:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, unsigned char*)'
  846 |     operator>>(basic_istream<char, _Traits>& __in, unsigned char* __s)
      |     ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:846:5: note:   template argument deduction/substitution failed:
foo.cc:6:11: note:   cannot convert '','' (type 'char') to type 'unsigned char*'
    6 |   cin>>a>>','>>b;
      |           ^~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:852:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, signed char*)'
  852 |     operator>>(basic_istream<char, _Traits>& __in, signed char* __s)
      |     ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:852:5: note:   template argument deduction/substitution failed:
foo.cc:6:11: note:   cannot convert '','' (type 'char') to type 'signed char*'
    6 |   cin>>a>>','>>b;
      |           ^~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:1006:5: note: candidate: 'template<class _Istream, class _Tp> _Istream&& std::operator>>(_Istream&&, _Tp&&)'
 1006 |     operator>>(_Istream&& __is, _Tp&& __x)
      |     ^~~~~~~~
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:1006:5: note:   template argument deduction/substitution failed:
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream: In substitution of 'template<class _Istream, class _Tp> _Istream&& std::operator>>(_Istream&&, _Tp&&) [with _Istream = std::basic_istream<char>&; _Tp = char]':
foo.cc:6:11:   required from here
/nix/store/h5kvfrjmpw792v8jg7nrzfkffmn0iyy8-gcc-12.3.0/include/c++/12.3.0/istream:1006:5: error: no type named 'type' in 'struct std::enable_if<false, void>'

[Hydro](https://hydro.ac)提供评测服务