#include <bits/stdc++.h>
using namespace std;
int main() {
  int h2, m2, h1, m1, a, b, d;
  char c;
  while (cin >> h2 >> c >> m2) {
    cin >> h1 >> c >> m1;
    a = (h2 * 60) + m2;
    b = (h1 * 60) + m1;
    if (a < b) a += (24 * 60);
    d = abs(a - b);
    printf("%02d%c%02d\n", d / 60, c, d % 60);
  }
  return 0;
}
