#include <bits/stdc++.h>
using namespace std;
int main() {
  int h1, m1, h2, m2;
  scanf("%d:%d %d:%d", &h1, &m1, &h2, &m2);
  if (m1 < m2) m1 += 60, h2++;
  if (h1 < h2) h1 += 24;
  printf("%.2d:%.2d\n", h1 - h2, m1 - m2);
  return 0;
}
