#include <bits/stdc++.h>
using namespace std;
int main() {
  int sh, sm, th, tm;
  scanf("%d:%d%d:%d", &sh, &sm, &th, &tm);
  int curr = sh * 60 + sm;
  int dur = th * 60 + tm;
  if (dur > curr) {
    dur = dur - curr;
    curr = 1440 - dur;
  } else {
    curr -= dur;
  }
  if (curr / 60 != 24)
    printf("%.2d:%.2d\n", curr / 60, curr % 60);
  else
    printf("00:%.2d", curr % 60);
  return 0;
}
