#include <bits/stdc++.h>
using namespace std;
int main() {
  int h1, m1, h2, m2, h, m;
  char c;
  cin >> h1 >> c >> m1 >> h2 >> c >> m2;
  if (h1 == 0) h1 = 24;
  if (h2 == 0) h2 = 24;
  h = h1 - h2;
  m = m1 - m2;
  if (m < 0) {
    h = h - 1;
    m = 60 + m;
  }
  if (h < 0) {
    h = h + 24;
  }
  if (h < 10 && m < 10) {
    cout << 0 << h << c << 0 << m << endl;
    return 0;
  }
  if (h < 10) {
    cout << 0 << h << c << m << endl;
    return 0;
  }
  if (m < 10) {
    cout << h << c << 0 << m << endl;
    return 0;
  }
  cout << h << c << m << endl;
  return 0;
}
