#include <bits/stdc++.h>
using namespace std;
int main() {
  int h1, m1, h2, m2, result1, result2;
  char c = ':';
  while (cin >> h1 >> c >> m1 >> h2 >> c >> m2) {
    if (m1 < m2) {
      h1 -= 1;
      m1 += 60;
    }
    result2 = m1 - m2;
    result1 = h1 - h2;
    if (result1 < 0) result1 += 24;
    if (result1 == 24) result1 = 0;
    cout << setw(2) << setfill('0') << abs(result1) << c << setw(2)
         << setfill('0') << abs(result2) << endl;
  }
  return 0;
}
