/in/foo.cc: In function 'int main()':
/in/foo.cc:6:8: error: 'cin' was not declared in this scope
    6 |  while(cin>>a>>b){
      |        ^~~
/in/foo.cc:2:1: note: 'std::cin' is defined in header '<iostream>'; did you forget to '#include <iostream>'?
    1 | #include <stdio.h>
  +++ |+#include <iostream>
    2 | using namespace std;
/in/foo.cc:7:3: error: 'cout' was not declared in this scope
    7 |   cout<<a-b<<endl:
      |   ^~~~
/in/foo.cc:7:3: note: 'std::cout' is defined in header '<iostream>'; did you forget to '#include <iostream>'?
/in/foo.cc:7:14: error: 'endl' was not declared in this scope
    7 |   cout<<a-b<<endl:
      |              ^~~~
/in/foo.cc:2:1: note: 'std::endl' is defined in header '<ostream>'; did you forget to '#include <ostream>'?
    1 | #include <stdio.h>
  +++ |+#include <ostream>
    2 | using namespace std;