#include <bits/stdc++.h>
int main() {
  int i, j, n;
  int h, m, hh, mm;
  scanf("%d:%d%d:%d", &h, &m, &hh, &mm);
  int ansh, ansm;
  ansm = m - mm;
  ansh = h - hh;
  if (ansm < 0) {
    ansm += 60;
    ansh -= 1;
  }
  if (ansh < 0) ansh += 24;
  if (ansh < 10) printf("0");
  printf("%d:", ansh);
  if (ansm < 10) printf("0");
  printf("%d\n", ansm);
  return 0;
}
