#include <bits/stdc++.h>
using namespace std;
int main() {
  long long i, hh, mm, h, m;
  char c;
  while (cin >> hh >> c >> mm) {
    cin >> h >> c >> m;
    long long w_time = hh * 60 + mm;
    long long s_time = h * 60 + m;
    long long time = w_time - s_time;
    if (time < 0) time = 24 * 60 + time;
    printf("%.2lld:%.2lld\n", time / 60, time % 60);
  }
  return 0;
}
