foo.cc: In function 'int main()':
foo.cc:6:9: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
    6 |         cin >> n >> m;
      |         ^~~
      |         std::cin
iostream:60:18: note: 'std::cin' declared here
foo.cc:9:17: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    9 |                 cout << 0;
      |                 ^~~~
      |                 std::cout
iostream:61:18: note: 'std::cout' declared here
foo.cc:19:33: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   19 |                                 cout << -1;
      |                                 ^~~~
      |                                 std::cout
iostream:61:18: note: 'std::cout' declared here
foo.cc:25:17: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   25 |                 cout << ans;
      |                 ^~~~
      |                 std::cout
iostream:61:18: note: 'std::cout' declared here

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