#include <bits/stdc++.h>
using namespace std;
int main() {
  int hr1, min1, hr2, min2;
  char str[6];
  cin >> str;
  hr1 = (str[0] - 48) * 10 + (str[1] - 48);
  min1 = (str[3] - 48) * 10 + (str[4] - 48);
  cin >> str;
  hr2 = (str[0] - 48) * 10 + (str[1] - 48);
  min2 = (str[3] - 48) * 10 + (str[4] - 48);
  if (min2 > min1) {
    min1 += 60;
    hr2++;
  }
  if (hr2 > hr1) hr1 += 24;
  int ans1 = hr1 - hr2;
  int ans2 = min1 - min2;
  if (ans1 < 10) cout << 0;
  cout << ans1 << ":";
  if (ans2 < 10) cout << 0;
  cout << ans2;
  return 0;
}
