#include <bits/stdc++.h>
using namespace std;
int main() {
  int x, y, a, b;
  scanf("%d:%d", &x, &y);
  scanf("%d:%d", &a, &b);
  int f, s;
  if (y < b) {
    s = y - b + 60;
    x--;
  } else
    s = y - b;
  if (x < a) {
    f = x - a + 24;
  } else
    f = x - a;
  if (f < 10)
    printf("0%d", f);
  else
    printf("%d", f);
  printf(":");
  if (s < 10)
    printf("0%d", s);
  else
    printf("%d", s);
  return 0;
}
