#include <bits/stdc++.h>
using namespace std;
int main() {
  int now = 0, dur = 0;
  int u, v;
  scanf("%d:%d", &u, &v);
  now = u * 60 + v;
  scanf("%d:%d", &u, &v);
  dur = u * 60 + v;
  now -= dur;
  now %= 24 * 60;
  if (now < 0) {
    now += 24 * 60;
  }
  int hh = now / 60;
  int mm = now % 60;
  printf("%02d:%02d\n", hh, mm);
  return 0;
}
