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>>a;
      |         ^~~
      |         std::cin
iostream:60:18: note: 'std::cin' declared here
foo.cc:8:9: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
    8 |         cout<<a<<endl;
      |         ^~~~
      |         std::cout
iostream:61:18: note: 'std::cout' declared here
foo.cc:8:18: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
    8 |         cout<<a<<endl;
      |                  ^~~~
      |                  std::endl
In file included from iostream:39:
/nix/store/l4dvshb0bw0ipyx17f6rknzk83mdx81y-gcc-11.3.0/include/c++/11.3.0/ostream:684:5: note: 'std::endl' declared here
  684 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~

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