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