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;
      |     ^~~
      |     std::cin
In file included from foo.cc:2:
/usr/include/c++/9/iostream:60:18: note: 'std::cin' declared here
   60 |   extern istream cin;  /// Linked to standard input
      |                  ^~~
foo.cc:6:12: error: 'n' was not declared in this scope
    6 |     cin >> n;
      |            ^
foo.cc:7:9: error: 'm' was not declared in this scope; did you mean 'tm'?
    7 |  cin >> m;
      |         ^
      |         tm
foo.cc:8:2: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    8 |  cout << n << m;
      |  ^~~~
      |  std::cout
In file included from foo.cc:2:
/usr/include/c++/9/iostream:61:18: note: 'std::cout' declared here
   61 |   extern ostream cout;  /// Linked to standard output
      |                  ^~~~

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