#include <bits/stdc++.h>
using namespace std;
int main() {
  string s, t;
  cin >> s >> t;
  int hour1 = (s[0] - '0') * 10 + s[1] - '0';
  int hour2 = (t[0] - '0') * 10 + t[1] - '0';
  int ans_hour = hour1 - hour2;
  if (ans_hour < 0) ans_hour += 24;
  int min1 = (s[3] - '0') * 10 + s[4] - '0';
  int min2 = (t[3] - '0') * 10 + t[4] - '0';
  int ans_min = min1 - min2;
  if (ans_min < 0) {
    ans_min += 60;
    ans_hour--;
  }
  if (ans_hour < 0) ans_hour += 24;
  if (ans_hour < 10) cout << 0;
  cout << ans_hour << ":";
  if (ans_min < 10) cout << 0;
  cout << ans_min;
  return 0;
}
