#include <bits/stdc++.h>
using namespace std;
int main() {
  int hour, minute, sleeph, sleepm;
  char temp;
  scanf("%d%c%d", &hour, &temp, &minute);
  scanf("%d%c%d", &sleeph, &temp, &sleepm);
  int shour, smin;
  smin = minute - sleepm;
  if (smin < 0) {
    smin += 60;
    hour--;
  }
  shour = hour - sleeph;
  while (shour < 0) {
    shour += 24;
  }
  if (shour < 10) cout << '0';
  cout << shour << ':';
  if (smin < 10) cout << '0';
  cout << smin << endl;
  return 0;
}
