foo.cc: In function ‘int main()’:
foo.cc:10:23: error: ‘No’ was not declared in this scope
   10 |                 cout<<No<<endl;
      |                       ^~
foo.cc:12:23: error: ‘Yes’ was not declared in this scope
   12 |                 cout<<Yes<<endl;
      |                       ^~~
foo.cc:20:31: error: ‘Yes’ was not declared in this scope
   20 |                         cout<<Yes<<endl;
      |                               ^~~
foo.cc:22:31: error: ‘No’ was not declared in this scope
   22 |                         cout<<No<<endl;
      |                               ^~