#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, c, d, t1, t2;
  while (scanf("%d:%d", &a, &b) != EOF) {
    scanf("%d:%d", &c, &d);
    t1 = b - d;
    t2 = a - c;
    if (t1 < 0) {
      t1 += 60;
      t2 -= 1;
    }
    if (t2 < 0) {
      t2 += 24;
    }
    printf("%02d:%02d\n", t2, t1);
  }
  return 0;
}
