foo.cc:16:2: error: 'cout' does not name a type
   16 |  cout << res;
      |  ^~~~
foo.cc:17:2: error: expected unqualified-id before 'return'
   17 |  return 0;
      |  ^~~~~~
foo.cc:18:1: error: expected declaration before '}' token
   18 | }
      | ^

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