#include <bits/stdc++.h>
using namespace std;
template <typename T>
inline ostream& operator<<(ostream& os, const vector<T>& v) {
  for (const auto& e : v) {
    cout << e;
  }
  cout << "\n";
  return os;
}
template <typename T>
inline istream& operator>>(istream& is, vector<T>& v) {
  for (auto& e : v) {
    cin >> e;
  }
  return is;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  int s, t;
  vector<char> sc(5), tc(5);
  cin >> sc >> tc;
  s = 600 * (sc[0] - '0') + 60 * (sc[1] - '0') + 10 * (sc[3] - '0') +
      (sc[4] - '0');
  t = 600 * (tc[0] - '0') + 60 * (tc[1] - '0') + 10 * (tc[3] - '0') +
      (tc[4] - '0');
  int p = (s - t + 1440) % 1440;
  vector<char> pc(5);
  pc[0] = '0' + p / 600;
  p %= 600;
  pc[1] = '0' + p / 60;
  p %= 60;
  pc[2] = ':';
  pc[3] = '0' + p / 10;
  p %= 10;
  pc[4] = '0' + p;
  cout << pc;
  return 0;
}
