#include <bits/stdc++.h>
using namespace std;
int sh, sm, eh, em, ans;
int main() {
  scanf("%d:%d%d:%d", &sh, &sm, &eh, &em);
  ans = (sh - eh) * 60 + sm - em;
  if (sh - eh < 0 || (sh - eh == 0 && sm - em < 0)) ans += 1440;
  if (ans / 60 < 10) printf("0");
  printf("%d:", ans / 60);
  if (ans % 60 < 10) printf("0");
  printf("%d", ans % 60);
  return 0;
}
