error: 'cout' was not declared in this scope; did you mean 'std::cout

  std::cout

In file included from /tmp/xXGSmzLhdM.cpp:2:

/usr/include/c++/11/iostream:61:18: note: 'std::cout' declared here

   61 |   extern ostream cout;          /// Linked to standard output

      |                  ^~~~

solution 

:- add namespace

using namespace std;