foo.cc: In function ‘int main()’:
foo.cc:6:5: error: ‘cin’ was not declared in this scope; did you mean ‘std::cin’?
    6 |     cin>>n>>m;
      |     ^~~
      |     std::cin
In file included from stdc++.h:146:
/nix/gcc-14.2.1.20250322/include/c++/14.2.1.20250322/iostream:62:18: note: ‘std::cin’ declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
foo.cc:27:13: error: ‘cout’ was not declared in this scope; did you mean ‘std::cout’?
   27 |             cout<<i+1;
      |             ^~~~
      |             std::cout
/nix/gcc-14.2.1.20250322/include/c++/14.2.1.20250322/iostream:63:18: note: ‘std::cout’ declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~