#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:500000000")
using namespace std;
int main() {
  string a, t;
  cin >> a >> t;
  for (int i = 0; i < 5; i++) a[i] -= '0', t[i] -= '0';
  int A = (a[0] * 10 + a[1]) * 60 + a[3] * 10 + a[4];
  int T = (t[0] * 10 + t[1]) * 60 + t[3] * 10 + t[4];
  int B = A - T;
  if (B < 0) B = 24 * 60 + B;
  printf("%02d:%02d\n", B / 60, B % 60);
}
