foo.cc: In function 'int main()':
foo.cc:3:9: error: 'cin' was not declared in this scope
    3 |         cin>>xmin>>xmax;
      |         ^~~
foo.cc:15:9: error: 'cout' was not declared in this scope
   15 |         cout<<sum<<endl;
      |         ^~~~
foo.cc:15:20: error: 'endl' was not declared in this scope
   15 |         cout<<sum<<endl;
      |                    ^~~~