#include <bits/stdc++.h>
using namespace std;
int main() {
  int h1, h2, hT;
  int m1, m2, mT;
  scanf("%d:%d", &h1, &m1);
  scanf("%d:%d", &h2, &m2);
  mT = m1 - m2;
  if (mT < 0) {
    mT += 60;
    --h1;
  }
  hT = h1 - h2;
  if (hT < 0) {
    hT += 24;
  }
  printf("%02d:%02d \n", hT, mT);
}
