/in/foo.cc: In function 'int main()':
/in/foo.cc:12:18: error: no match for 'operator<<' (operand types are 'std::basic_ostream<char>' and '<unresolved overloaded function type>')
   12 |         cout<<sum<<end;
      |         ~~~~~~~~~^~~~~
In file included from /usr/include/c++/12/istream:39,
                 from /usr/include/c++/12/sstream:38,
                 from /usr/include/c++/12/complex:45,
                 from /usr/include/c++/12/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/12/bits/stdc++.h:54,
                 from /in/foo.cc:1:
/usr/include/c++/12/ostream:108:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(__ostream_type& (*)(__ostream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>]'
  108 |       operator<<(__ostream_type& (*__pf)(__ostream_type&))
      |       ^~~~~~~~
/usr/include/c++/12/ostream:108:36: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'std::basic_ostream<char>::__ostream_type& (*)(std::basic_ostream<char>::__ostream_type&)' {aka 'std::basic_ostream<char>& (*)(std::basic_ostream<char>&)'}
  108 |       operator<<(__ostream_type& (*__pf)(__ostream_type&))
      |                  ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/12/ostream:117:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(__ios_type& (*)(__ios_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>; __ios_type = std::basic_ios<char>]'
  117 |       operator<<(__ios_type& (*__pf)(__ios_type&))
      |       ^~~~~~~~
/usr/include/c++/12/ostream:117:32: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'std::basic_ostream<char>::__ios_type& (*)(std::basic_ostream<char>::__ios_type&)' {aka 'std::basic_ios<char>& (*)(std::basic_ios<char>&)'}
  117 |       operator<<(__ios_type& (*__pf)(__ios_type&))
      |                  ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~
/usr/include/c++/12/ostream:127:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(std::ios_base& (*)(std::ios_base&)) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>]'
  127 |       operator<<(ios_base& (*__pf) (ios_base&))
      |       ^~~~~~~~
/usr/include/c++/12/ostream:127:30: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'std::ios_base& (*)(std::ios_base&)'
  127 |       operator<<(ios_base& (*__pf) (ios_base&))
      |                  ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
/usr/include/c++/12/ostream:166:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long int) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>]'
  166 |       operator<<(long __n)
      |       ^~~~~~~~
/usr/include/c++/12/ostream:166:23: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'long int'
  166 |       operator<<(long __n)
      |                  ~~~~~^~~
/usr/include/c++/12/ostream:170:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long unsigned int) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>]'
  170 |       operator<<(unsigned long __n)
      |       ^~~~~~~~
/usr/include/c++/12/ostream:170:32: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'long unsigned int'
  170 |       operator<<(unsigned long __n)
      |                  ~~~~~~~~~~~~~~^~~
/usr/include/c++/12/ostream:174:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(bool) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>]'
  174 |       operator<<(bool __n)
      |       ^~~~~~~~
/usr/include/c++/12/ostream:174:23: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'bool'
  174 |       operator<<(bool __n)
      |                  ~~~~~^~~
In file included from /usr/include/c++/12/ostream:833:
/usr/include/c++/12/bits/ostream.tcc:91:5: note: candidate: 'std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(short int) [with _CharT = char; _Traits = std::char_traits<char>]'
   91 |     basic_ostream<_CharT, _Traits>::
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/12/bits/ostream.tcc:92:22: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'short int'
   92 |     operator<<(short __n)
      |                ~~~~~~^~~
/usr/include/c++/12/ostream:181:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(short unsigned int) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>]'
  181 |       operator<<(unsigned short __n)
      |       ^~~~~~~~
/usr/include/c++/12/ostream:181:33: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'short unsigned int'
  181 |       operator<<(unsigned short __n)
      |                  ~~~~~~~~~~~~~~~^~~
/usr/include/c++/12/bits/ostream.tcc:105:5: note: candidate: 'std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(int) [with _CharT = char; _Traits = std::char_traits<char>]'
  105 |     basic_ostream<_CharT, _Traits>::
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/12/bits/ostream.tcc:106:20: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'int'
  106 |     operator<<(int __n)
      |                ~~~~^~~
/usr/include/c++/12/ostream:192:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(unsigned int) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>]'
  192 |       operator<<(unsigned int __n)
      |       ^~~~~~~~
/usr/include/c++/12/ostream:192:31: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'unsigned int'
  192 |       operator<<(unsigned int __n)
      |                  ~~~~~~~~~~~~~^~~
/usr/include/c++/12/ostream:201:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long long int) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>]'
  201 |       operator<<(long long __n)
      |       ^~~~~~~~
/usr/include/c++/12/ostream:201:28: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'long long int'
  201 |       operator<<(long long __n)
      |                  ~~~~~~~~~~^~~
/usr/include/c++/12/ostream:205:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long long unsigned int) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>]'
  205 |       operator<<(unsigned long long __n)
      |       ^~~~~~~~
/usr/include/c++/12/ostream:205:37: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'long long unsigned int'
  205 |       operator<<(unsigned long long __n)
      |                  ~~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/12/ostream:220:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(double) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>]'
  220 |       operator<<(double __f)
      |       ^~~~~~~~
/usr/include/c++/12/ostream:220:25: note:   no known conversion for argument 1 from '<unresol