#include <bits/stdc++.h>
using namespace std;
int main(void) {
  int minutes_day = 1440;
  char curr_time[6], sleep_time[6];
  int time, sleep, bedtime;
  cin >> curr_time;
  cin >> sleep_time;
  time = 10 * (curr_time[3] - 48) + (curr_time[4] - 48) +
         60 * (10 * (curr_time[0] - 48) + (curr_time[1] - 48));
  sleep = 10 * (sleep_time[3] - 48) + (sleep_time[4] - 48) +
          60 * (10 * (sleep_time[0] - 48) + (sleep_time[1] - 48));
  if (time == sleep) {
    cout << "00:00" << endl;
    return 0;
  }
  bedtime = time - sleep;
  bedtime = bedtime > 0 ? bedtime : bedtime + minutes_day;
  int hours = bedtime / 60;
  int minutes = bedtime - hours * 60;
  if (hours < 10) cout << "0";
  cout << hours << ":";
  if (minutes < 10) cout << "0";
  cout << minutes << endl;
  return 0;
}
