Language: C++

#include<bits/stdc++.h>
using namespace; std;
int main(){
  int N; int M; cin>>N>>M;
  vector<int> S(M);
  for(int i=0; i<M; i++){
    cin>>S.at(i);
    N-=S.at(i);
  }
  if(N>=0)
    cout<<N<<endl;
  else cout<<-1<<endl;
}

Compiler output:
a.cc:2:16: error: expected identifier before ';' token
    2 | using namespace; std;
      |                ^
a.cc:2:18: error: 'std' does not name a type
    2 | using namespace; std;
      |                  ^~~
a.cc: In function 'int main()':
a.cc:4:17: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    4 |   int N; int M; cin>>N>>M;
      |                 ^~~
      |                 std::cin
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:146,
                 from a.cc:1:
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:5:3: error: 'vector' was not declared in this scope
    5 |   vector<int> S(M);
      |   ^~~~~~
a.cc:5:3: note: suggested alternatives:
In file included from /usr/include/c++/14/vector:66,
                 from /usr/include/c++/14/functional:64,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:53:
/usr/include/c++/14/bits/stl_vector.h:428:11: note:   'std::vector'
  428 |     class vector : protected _Vector_base<_Tp, _Alloc>
      |           ^~~~~~
/usr/include/c++/14/vector:93:13: note:   'std::pmr::vector'
   93 |       using vector = std::vector<_Tp, polymorphic_allocator<_Tp>>;
      |             ^~~~~~
a.cc:5:10: error: expected primary-expression before 'int'
    5 |   vector<int> S(M);
      |          ^~~
a.cc:7:10: error: 'S' was not declared in this scope
    7 |     cin>>S.at(i);
      |          ^
a.cc:11:5: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   11 |     cout<<N<<endl;
      |     ^~~~
      |     std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:11:14: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   11 |     cout<<N<<endl;
      |              ^~~~
      |              std::endl
In file included from /usr/include/c++/14/istream:41,
                 from /usr/include/c++/14/sstream:40,
                 from /usr/include/c++/14/complex:45,
                 from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127:
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:12:8: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   12 |   else cout<<-1<<endl;
      |        ^~~~
      |        std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:12:18: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   12 |   else cout<<-1<<endl;
      |                  ^~~~
      |                  std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~