#include <bits/stdc++.h>
using namespace std;
int main() {
  char p;
  int a, b, c, d;
  cin >> a >> p >> b >> c >> p >> d;
  pair<int, int> s(b, a), t(d, c), res;
  res.first = s.first - t.first;
  if (res.first < 0) {
    res.first += 60;
    s.second--;
  }
  res.second = s.second - t.second;
  if (res.second < 0) {
    res.second += 24;
  }
  if (res.second < 10) {
    cout << 0;
  }
  cout << res.second << ':';
  if (res.first < 10) {
    cout << '0';
  }
  cout << res.first;
}
