#include <bits/stdc++.h>
using namespace std;
const int mod = 1e9 + 7;
void inc(int& a, int b) {
  a += b;
  if (a > mod) a -= mod;
}
int bin(int a, int n) {
  int res = 1;
  while (n) {
    if (n & 1) res = (1ll * res * a) % mod;
    a = (1ll * a * a) % mod;
    n >>= 1;
  }
  return res;
}
int main() {
  string s1, s2;
  int h1, m1, h2, m2;
  scanf("%d:%d", &h1, &m1);
  scanf("%d:%d", &h2, &m2);
  h1 -= h2;
  m1 -= m2;
  if (m1 < 0) h1--, m1 += 60;
  if (h1 < 0) h1 += 24;
  printf("%02d:%02d", h1, m1);
  return 0;
}
