/in/foo.cc: In function 'int main()':
/in/foo.cc:10:6: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   10 |      cout<<k<<j<<i<<endl;
      |      ^~~~
      |      std::cout
In file included from /in/foo.cc:1:
/usr/include/c++/9/iostream:61:18: note: 'std::cout' declared here
   61 |   extern ostream cout;  /// Linked to standard output
      |                  ^~~~
/in/foo.cc:10:21: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   10 |      cout<<k<<j<<i<<endl;
      |                     ^~~~
      |                     std::endl
In file included from /usr/include/c++/9/iostream:39,
                 from /in/foo.cc:1:
/usr/include/c++/9/ostream:599:5: note: 'std::endl' declared here
  599 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
/in/foo.cc:5:9: warning: unused variable 'a' [-Wunused-variable]
    5 |     int a,b,c;
      |         ^
/in/foo.cc:5:11: warning: unused variable 'b' [-Wunused-variable]
    5 |     int a,b,c;
      |           ^
/in/foo.cc:5:13: warning: unused variable 'c' [-Wunused-variable]
    5 |     int a,b,c;
      |             ^