#include <bits/stdc++.h>
using namespace std;
int main() {
  string str1, str2;
  cin >> str2 >> str1;
  int hr1 = (int)(str1[0] - '0') * 10 + (int)(str1[1] - '0');
  int min1 = (int)(str1[3] - '0') * 10 + (int)(str1[4] - '0');
  int hr2 = (int)(str2[0] - '0') * 10 + (int)(str2[1] - '0');
  int min2 = (int)(str2[3] - '0') * 10 + (int)(str2[4] - '0');
  int minx = min2 - min1;
  int hrx = hr2 - hr1;
  if (minx < 0) {
    hrx--;
    minx = 60 + minx;
  }
  if (hrx < 0) {
    hrx = 24 + hrx;
  }
  if (hrx < 10)
    cout << 0 << hrx;
  else
    cout << hrx;
  cout << ":";
  if (minx < 10)
    cout << 0 << minx;
  else
    cout << minx;
  return 0;
}
