#include <bits/stdc++.h>
using namespace std;
int main() {
  char h1, h2, m1, m2;
  char sh1, sh2, sm1, sm2;
  char lel;
  cin >> h1 >> h2 >> lel >> m1 >> m2;
  cin >> sh1 >> sh2 >> lel >> sm1 >> sm2;
  int ch = 10 * ((int)h1 - '0') + ((int)h2 - '0');
  int cm = 10 * ((int)m1 - '0') + ((int)m2 - '0');
  int sh = 10 * ((int)sh1 - '0') + ((int)sh2 - '0');
  int sm = 10 * ((int)sm1 - '0') + ((int)sm2 - '0');
  int rh = (ch - sh) % 24;
  int rm = (cm - sm) % 60;
  if (rh < 0) rh += 24;
  if (rm < 0) rm += 60;
  if (cm < sm) {
    rh = (rh - 1) % 24;
    if (rh < 0) rh += 24;
  }
  if (rh < 10) {
    cout << "0" << rh << ":";
  } else {
    cout << rh << ":";
  }
  if (rm < 10) {
    cout << "0" << rm << endl;
  } else {
    cout << rm << endl;
  }
  return 0;
}
