#include <bits/stdc++.h>
using namespace std;
int main() {
  string t1, t2;
  cin >> t1 >> t2;
  int h1 = std::atoi(t1.substr(0, 2).c_str());
  int h2 = std::atoi(t2.substr(0, 2).c_str());
  int m1 = std::atoi(t1.substr(3, 5).c_str());
  int m2 = std::atoi(t2.substr(3, 5).c_str());
  int hp = h1 - h2;
  int mp = m1 - m2;
  if (mp < 0) {
    mp += 60;
    hp--;
  }
  if (hp < 0) hp += 24;
  (hp < 10) ? cout << 0 << hp : cout << hp;
  cout << ':';
  (mp < 10) ? cout << 0 << mp : cout << mp;
  return 0;
}
