foo.cc: In function 'int main()':
foo.cc:7:9: error: 'cin' was not declared in this scope
    7 |         cin>>a;
      |         ^~~
foo.cc:8:15: error: 'add' was not declared in this scope
    8 |         int c=add(b);
      |               ^~~
foo.cc:11:17: error: 'cout' was not declared in this scope
   11 |                 cout<<c<<endl;
      |                 ^~~~
foo.cc:11:26: error: 'endl' was not declared in this scope
   11 |                 cout<<c<<endl;
      |                          ^~~~

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