#include <bits/stdc++.h>
using namespace std;
int main() {
  long long t1, t2, v1, v2, t, v, ans, a, b;
  char c;
  cin >> t1 >> c >> t2;
  cin >> v1 >> c >> v2;
  t = t1 * 60 + t2;
  v = v1 * 60 + v2;
  if (t < v) t = t + (24 * 60);
  a = abs(t - v) / 60;
  b = abs(t - v) % 60;
  if (a < 10)
    cout << 0 << a << ":";
  else
    cout << a << ":";
  if (b < 10)
    cout << 0 << b << endl;
  else
    cout << b << endl;
  return 0;
}
