foo.cc: In function ‘int main()’:
foo.cc:43:5: error: ‘cin’ was not declared in this scope
   43 |     cin >> m1 >> d1;
      |     ^~~
foo.cc:2:1: note: ‘std::cin’ is defined in header ‘<iostream>’; did you forget to ‘#include <iostream>’?
    1 | #include <cstdio>
  +++ |+#include <iostream>
    2 | using namespace std;
foo.cc:51:5: error: ‘cout’ was not declared in this scope
   51 |     cout << d2 - d1;
      |     ^~~~
foo.cc:51:5: note: ‘std::cout’ is defined in header ‘<iostream>’; did you forget to ‘#include <iostream>’?