Language: C++

#include<iostream>
#include<vector>

using namespace std;

int main()
{
  int n,m;
  cin >> m >> n;
  cerr << m >> " " << n << endl;
  vector<int> per;
  vector<vector<int> > G;
  G.resize(m);
  bool used[m]; 
  per.resize(m);
  for(int i=0;i<m;i++)
    per[i] = 0,used[i] = false;
  for(int i=0;i<n;i++)
    {
      int x,y;
      cin >> x >> y;
      cerr << x << " "  << y << endl;
      x--,y--;
      per[y]++;
      G[x].push_back(y);
    }
  
  
  
  for(int i=0;i<n;i++)
    {
      for(int j=0;j<n;j++)
	{
	  if(used[j])
	    continue;
	  if(!per[j])
	    {
	      cout << j+1 << endl;
	      used[j] = true;
	      for(int k=0;k<G[j].size();k++)
		per[G[j][k]]--;
	      break;
	    }
	}
    }
  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:10:13: error: no match for 'operator>>' (operand types are 'std::basic_ostream<char>' and 'const char [2]')
   10 |   cerr << m >> " " << n << endl;
      |   ~~~~~~~~~ ^~ ~~~
      |        |       |
      |        |       const char [2]
      |        std::basic_ostream<char>
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:10:16: note:   'std::basic_ostream<char>' is not derived from 'std::basic_istream<_CharT, _Traits>'
   10 |   cerr << m >> " " << n << 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:10:8: note:   cannot convert 'std::cerr.std::basic_ostream<char>::operator<<(m)' (type 'std::basic_ostream<char>') to type 'std::byte'
   10 |   cerr << m >> " " << n << 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:10:16: note:   'std::basic_ostream<char>' is not derived from 'std::basic_istream<_CharT, _Traits>'
   10 |   cerr << m >> " " << n << 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:10:16: note:   'std::basic_ostream<char>' is not derived from 'std::basic_istream<char, _Traits>'
   10 |   cerr << m >> " " << n << 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:10:16: note:   'std::basic_ostream<char>' is not derived from 'std::basic_istream<char, _Traits>'
   10 |   cerr << m >> " " << n << 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:10:16: note:   'std::basic_ostream<char>' is not derived from 'std::basic_istream<_CharT, _Traits>'
   10 |   cerr << m >> " " << n << 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:10:16: note:   'std::basic_ostream<char>' is not derived from 'std::basic_istream<char, _Traits>'
   10 |   cerr << m >> " " << n << 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:10:16: note:   'std::basic_ostream<char>' is not derived from 'std::basic_istream<char, _Traits>'
   10 |   cerr << m >> " " << n << 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:
/usr/include/c++/14/istream: In substitution of 'template<class _Istream, class _Tp> _Istream&& std::operator>>(_Istream&&, _Tp&&) [with _Istream = std::basic_ostream<char>&; _Tp = const char (&)[2]]':
a.cc:10:16:   required from here
   10 |   cerr << m >> " " << n << endl;
      |                ^~~
/usr/include/c++/14/istream:1099:5: error: no type named 'type' in 'struct std::enable_if<false, void>'
 1099 |     operator>>(_Istream&& __is, _Tp&& __x)
      |     ^~~~~~~~