#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, c, d;
  int a1, b1, c1, d1;
  scanf("%d:%d", &a, &c);
  scanf("%d:%d", &a1, &c1);
  int a2, b2, c2, d2;
  bool flag = false;
  if (c - c1 >= 0)
    c2 = c - c1;
  else
    flag = true, c2 = c + 60 - c1;
  if (flag) a--;
  a2 = ((a + 24) - a1) % 24;
  if (a2 / 10 == 0)
    printf("0%d:", a2);
  else
    printf("%d%d:", a2 / 10, a2 % 10);
  if (c2 / 10 == 0)
    printf("0%d\n", c2);
  else
    printf("%d%d\n", c2 / 10, c2 % 10);
  return 0;
}
