#include <bits/stdc++.h>
using namespace std;
int main() {
  int h1, t1, h2, t2, ansh, anst;
  scanf("%2d:%2d", &h1, &t1);
  scanf("%2d:%2d", &h2, &t2);
  if (t1 < t2) {
    h1--, t1 += 60;
  }
  anst = t1 - t2;
  ansh = h1 - h2;
  if (ansh < 0) ansh += 24;
  printf("%02d:%02d\n", ansh, anst);
  return 0;
}
