#include <bits/stdc++.h>
using namespace std;
int main() {
  char ch;
  int a, b, c, d, time, ans;
  cin >> a >> ch >> b;
  cin >> c >> ch >> d;
  if (b >= d)
    time = b - d;
  else {
    b = b + 60;
    time = b - d;
    a = a - 1;
  }
  if (a >= c)
    ans = a - c;
  else {
    a = a + 24;
    ans = a - c;
  }
  if (ans < 10)
    cout << "0" << ans << ":";
  else
    cout << ans << ":";
  if (time < 10)
    cout << "0" << time;
  else
    cout << time;
  return 0;
}
