foo.cc: In function 'int main()':
foo.cc:6:7: error: no match for 'operator>' (operand types are 'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} and 'int')
    6 | cin>>a>b;
      | ~~~~~~^~
      |    |   |
      |    |   int
      |    std::basic_istream<char>::__istream_type {aka std::basic_istream<char>}
foo.cc:6:7: note: candidate: 'operator>(int, int)' <built-in>
    6 | cin>>a>b;
      | ~~~~~~^~
foo.cc:6:7: 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 /usr/include/c++/9/bits/stl_algobase.h:64,
                 from /usr/include/c++/9/bits/char_traits.h:39,
                 from /usr/include/c++/9/ios:40,
                 from /usr/include/c++/9/ostream:38,
                 from /usr/include/c++/9/iostream:39,
                 from foo.cc:1:
/usr/include/c++/9/bits/stl_pair.h:467:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator>(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&)'
  467 |     operator>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/9/bits/stl_pair.h:467:5: note:   template argument deduction/substitution failed:
foo.cc:6:8: note:   'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} is not derived from 'const std::pair<_T1, _T2>'
    6 | cin>>a>b;
      |        ^
In file included from /usr/include/c++/9/bits/stl_algobase.h:67,
                 from /usr/include/c++/9/bits/char_traits.h:39,
                 from /usr/include/c++/9/ios:40,
                 from /usr/include/c++/9/ostream:38,
                 from /usr/include/c++/9/iostream:39,
                 from foo.cc:1:
/usr/include/c++/9/bits/stl_iterator.h:343:5: note: candidate: 'template<class _Iterator> bool std::operator>(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_Iterator>&)'
  343 |     operator>(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/9/bits/stl_iterator.h:343:5: note:   template argument deduction/substitution failed:
foo.cc:6:8: note:   'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} is not derived from 'const std::reverse_iterator<_Iterator>'
    6 | cin>>a>b;
      |        ^
In file included from /usr/include/c++/9/bits/stl_algobase.h:67,
                 from /usr/include/c++/9/bits/char_traits.h:39,
                 from /usr/include/c++/9/ios:40,
                 from /usr/include/c++/9/ostream:38,
                 from /usr/include/c++/9/iostream:39,
                 from foo.cc:1:
/usr/include/c++/9/bits/stl_iterator.h:381:5: note: candidate: 'template<class _IteratorL, class _IteratorR> bool std::operator>(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_IteratorR>&)'
  381 |     operator>(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/9/bits/stl_iterator.h:381:5: note:   template argument deduction/substitution failed:
foo.cc:6:8: note:   'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} is not derived from 'const std::reverse_iterator<_Iterator>'
    6 | cin>>a>b;
      |        ^
In file included from /usr/include/c++/9/bits/stl_algobase.h:67,
                 from /usr/include/c++/9/bits/char_traits.h:39,
                 from /usr/include/c++/9/ios:40,
                 from /usr/include/c++/9/ostream:38,
                 from /usr/include/c++/9/iostream:39,
                 from foo.cc:1:
/usr/include/c++/9/bits/stl_iterator.h:1184:5: note: candidate: 'template<class _IteratorL, class _IteratorR> bool std::operator>(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorR>&)'
 1184 |     operator>(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/9/bits/stl_iterator.h:1184:5: note:   template argument deduction/substitution failed:
foo.cc:6:8: note:   'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} is not derived from 'const std::move_iterator<_IteratorL>'
    6 | cin>>a>b;
      |        ^
In file included from /usr/include/c++/9/bits/stl_algobase.h:67,
                 from /usr/include/c++/9/bits/char_traits.h:39,
                 from /usr/include/c++/9/ios:40,
                 from /usr/include/c++/9/ostream:38,
                 from /usr/include/c++/9/iostream:39,
                 from foo.cc:1:
/usr/include/c++/9/bits/stl_iterator.h:1190:5: note: candidate: 'template<class _Iterator> bool std::operator>(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorL>&)'
 1190 |     operator>(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/9/bits/stl_iterator.h:1190:5: note:   template argument deduction/substitution failed:
foo.cc:6:8: note:   'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} is not derived from 'const std::move_iterator<_IteratorL>'
    6 | cin>>a>b;
      |        ^
In file included from /usr/include/c++/9/string:55,
                 from /usr/include/c++/9/bits/locale_classes.h:40,
                 from /usr/include/c++/9/bits/ios_base.h:41,
                 from /usr/include/c++/9/ios:42,
                 from /usr/include/c++/9/ostream:38,
                 from /usr/include/c++/9/iostream:39,
                 from foo.cc:1:
/usr/include/c++/9/bits/basic_string.h:6267:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator>(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&, const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&)'
 6267 |     operator>(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/9/bits/basic_string.h:6267:5: note:   template argument deduction/substitution failed:
foo.cc:6:8: note:   'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>'
    6 | cin>>a>b;
      |        ^
In file included from /usr/include/c++/9/string:55,
                 from /usr/include/c++/9/bits/locale_classes.h:40,
                 from /usr/include/c++/9/bits/ios_base.h:41,
                 from /usr/include/c++/9/ios:42,
                 from /usr/include/c++/9/ostream:38,
                 from /usr/include/c++/9/iostream:39,
                 from foo.cc:1:
/usr/include/c++/9/bits/basic_string.h:6280:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator>(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*)'
 6280 |     operator>(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/9/bits/basic_string.h:6280:5: note:   template argument deduction/substitution failed:
foo.cc:6:8: note:   'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} is not derived from 'const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>'
    6 | cin>>a>b;
      |        ^
In file included from /usr/include/c++/9/string:55,
                 from /usr/include/c++/9/bits/locale_classes.h:40,
                 from /usr/include/c++/9/bits/ios_base.h:41,
                 from /usr/include/c++/9/ios:42,
                 from /usr/include/c++/9/ostream:38,
                 from /usr/include/c++/9/iostream:39,
                 from foo.cc:1:
/usr/include/c++/9/bits/basic_string.h:6292:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator>(const _CharT*, const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&)'
 6292 |     operator>(const _CharT* __lhs,
      |     ^~~~~~~~
/usr/include/c++/9/bits/basic_string.h:6292:5: note:   template argument deduction/substitution failed:
foo.cc:6:8: note:   mismatched types 'const _CharT*' and 'std::basic_istream<char>'
    6 | cin>>a>b;
      |        ^
foo.cc:7:10: error: expected ';' before ':' token
    7 | cout<<a+b:
      |          ^
      |          ;

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