Language: C++

#include<iostream>
using namespace std;
#include<string>
int main(){
string A,B;
  cin >> A,B >> endl;
  if(A=1,B=2){
  cout << "3" << endl;
  }
  if(A=1,B=3){
  cout << "2" << endl;
  }
  if(A=2,B=1){
  cout << "3" << endl;
  }
  if(A=2,B=3){
  cout << "1" << endl;
  }
  if(A=3,B=1){
  cout << "2" << endl;
  }
  if(A=3,B=2){
  cout << "1" << endl;
  }
}

Compiler output:
a.cc: In function 'int main()':
a.cc:6:14: error: no match for 'operator>>' (operand types are 'std::string' {aka 'std::__cxx11::basic_string<char>'} and '<unresolved overloaded function type>')
    6 |   cin >> A,B >> endl;
      |            ~~^~~~~~~
In file included from /usr/include/c++/14/string:55,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/basic_string.tcc:835:5: 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, _Allocator>&)'
  835 |     operator>>(basic_istream<_CharT, _Traits>& __in,
      |     ^~~~~~~~
/usr/include/c++/14/bits/basic_string.tcc:835:5: note:   template argument deduction/substitution failed:
a.cc:6:17: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'std::basic_istream<_CharT, _Traits>'
    6 |   cin >> A,B >> endl;
      |                 ^~~~
In file included from /usr/include/c++/14/bits/memory_resource.h:38,
                 from /usr/include/c++/14/string:68:
/usr/include/c++/14/cstddef:131:5: note: candidate: 'template<class _IntegerType> constexpr std::__byte_op_t<_IntegerType> std::operator>>(byte, _IntegerType)'
  131 |     operator>>(byte __b, _IntegerType __shift) noexcept
      |     ^~~~~~~~
/usr/include/c++/14/cstddef:131:5: note:   template argument deduction/substitution failed:
a.cc:6:17: note:   couldn't deduce template parameter '_IntegerType'
    6 |   cin >> A,B >> endl;
      |                 ^~~~
In file included from /usr/include/c++/14/istream:1109,
                 from /usr/include/c++/14/iostream:42:
/usr/include/c++/14/bits/istream.tcc:978:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(basic_istream<_CharT, _Traits>&, _CharT&)'
  978 |     operator>>(basic_istream<_CharT, _Traits>& __in, _CharT& __c)
      |     ^~~~~~~~
/usr/include/c++/14/bits/istream.tcc:978:5: note:   template argument deduction/substitution failed:
a.cc:6:17: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'std::basic_istream<_CharT, _Traits>'
    6 |   cin >> A,B >> endl;
      |                 ^~~~
/usr/include/c++/14/istream:849:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, unsigned char&)'
  849 |     operator>>(basic_istream<char, _Traits>& __in, unsigned char& __c)
      |     ^~~~~~~~
/usr/include/c++/14/istream:849:5: note:   template argument deduction/substitution failed:
a.cc:6:17: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'std::basic_istream<char, _Traits>'
    6 |   cin >> A,B >> endl;
      |                 ^~~~
/usr/include/c++/14/istream:854:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, signed char&)'
  854 |     operator>>(basic_istream<char, _Traits>& __in, signed char& __c)
      |     ^~~~~~~~
/usr/include/c++/14/istream:854:5: note:   template argument deduction/substitution failed:
a.cc:6:17: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'std::basic_istream<char, _Traits>'
    6 |   cin >> A,B >> endl;
      |                 ^~~~
/usr/include/c++/14/istream:896:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_istream<_CharT, _Traits>& std::operator>>(basic_istream<_CharT, _Traits>&, _CharT*)'
  896 |     operator>>(basic_istream<_CharT, _Traits>& __in, _CharT* __s)
      |     ^~~~~~~~
/usr/include/c++/14/istream:896:5: note:   template argument deduction/substitution failed:
a.cc:6:17: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'std::basic_istream<_CharT, _Traits>'
    6 |   cin >> A,B >> endl;
      |                 ^~~~
/usr/include/c++/14/istream:939:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, unsigned char*)'
  939 |     operator>>(basic_istream<char, _Traits>& __in, unsigned char* __s)
      |     ^~~~~~~~
/usr/include/c++/14/istream:939:5: note:   template argument deduction/substitution failed:
a.cc:6:17: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'std::basic_istream<char, _Traits>'
    6 |   cin >> A,B >> endl;
      |                 ^~~~
/usr/include/c++/14/istream:945:5: note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(basic_istream<char, _Traits>&, signed char*)'
  945 |     operator>>(basic_istream<char, _Traits>& __in, signed char* __s)
      |     ^~~~~~~~
/usr/include/c++/14/istream:945:5: note:   template argument deduction/substitution failed:
a.cc:6:17: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'std::basic_istream<char, _Traits>'
    6 |   cin >> A,B >> endl;
      |                 ^~~~
/usr/include/c++/14/istream:1099:5: note: candidate: 'template<class _Istream, class _Tp> _Istream&& std::operator>>(_Istream&&, _Tp&&)'
 1099 |     operator>>(_Istream&& __is, _Tp&& __x)
      |     ^~~~~~~~
/usr/include/c++/14/istream:1099:5: note:   template argument deduction/substitution failed:
a.cc:6:17: note:   couldn't deduce template parameter '_Tp'
    6 |   cin >> A,B >> endl;
      |                 ^~~~
a.cc:7:9: error: could not convert '(((void)A.std::__cxx11::basic_string<char>::operator=(1)), B.std::__cxx11::basic_string<char>::operator=(2))' from 'std::__cxx11::basic_string<char>' to 'bool'
    7 |   if(A=1,B=2){
      |      ~~~^~~~
      |         |
      |         std::__cxx11::basic_string<char>
a.cc:10:9: error: could not convert '(((void)A.std::__cxx11::basic_string<char>::operator=(1)), B.std::__cxx11::basic_string<char>::operator=(3))' from 'std::__cxx11::basic_string<char>' to 'bool'
   10 |   if(A=1,B=3){
      |      ~~~^~~~
      |         |
      |         std::__cxx11::basic_string<char>
a.cc:13:9: error: could not convert '(((void)A.std::__cxx11::basic_string<char>::operator=(2)), B.std::__cxx11::basic_string<char>::operator=(1))' from 'std::__cxx11::basic_string<char>' to 'bool'
   13 |   if(A=2,B=1){
      |      ~~~^~~~
      |         |
      |         std::__cxx11::basic_string<char>
a.cc:16:9: error: could not convert '(((void)A.std::__cxx11::basic_string<char>::operator=(2)), B.std::__cxx11::basic_string<char>::operator=(3))' from 'std::__cxx11::basic_string<char>' to 'bool'
   16 |   if(A=2,B=3){
      |      ~~~^~~~
      |         |
      |         std::__cxx11::basic_string<char>
a.cc:19:9: error: could not convert '(((void)A.std::__cxx11::basic_string<char>::operator=(3)), B.std::__cxx11::basic_string<char>::operator=(1))' from 'std::__cxx11::basic_string<char>' to 'bool'
   19 |   if(A=3,B=1){
      |      ~~~^~~~
      |         |
      |         std::__cxx11::basic_string<char>
a.cc:22:9: error: could not convert '(((void)A.std::__cxx11::basic_string<char>::operator=(3)), B.std::__cxx11::basic_string<char>::operator=(2))' from 'std::__cxx11::basic_string<char>' to 'bool'
   22 |   if(A=3,B=2){
      |      ~~~^~~~
      |         |
      |         std::__cxx11::basic_string<char>