#include <bits/stdc++.h>
using namespace std;
int main() {
  int s1, s2, t1, t2;
  char ch1, ch2;
  cin >> s1 >> ch1 >> s2;
  cin >> t1 >> ch2 >> t2;
  int a = s1 - t1;
  int b = s2 - t2;
  if (b < 0) {
    b += 60;
    a--;
  }
  if (a < 0) {
    a += 24;
  }
  cout << right << setw(2) << setfill('0') << a << ":";
  cout << right << setw(2) << setfill('0') << b << endl;
  return 0;
}
