#include <bits/stdc++.h>
using namespace std;
int main() {
  int a[2] = {0, 0};
  for (int i = 0; i < 2; i++) {
    string s;
    cin >> s;
    for (int j = 0; j < 5; j++) {
      if (j == 2) continue;
      s[j] -= '0';
      a[i] = a[i] * 10 + s[j];
    }
  }
  if (a[0] < a[1]) a[0] += 2400;
  int hh = 0, mm;
  mm = a[0] % 100 - a[1] % 100;
  if (a[0] % 100 < a[1] % 100) hh = -1, mm += 60;
  hh += a[0] / 100 - a[1] / 100;
  if (hh < 10) cout << 0;
  cout << hh << ':';
  if (mm < 10) cout << 0;
  cout << mm << endl;
}
