#include <bits/stdc++.h>
using namespace std;
int main() {
  string s, t;
  cin >> s >> t;
  int hs, ms, ht, mt;
  hs = ms = ht = mt = 0;
  for (int i = 0; i < 2; i++) {
    hs = hs * 10 + (s[i] - '0');
    ms = ms * 10 + (s[i + 3] - '0');
    ht = ht * 10 + (t[i] - '0');
    mt = mt * 10 + (t[i + 3] - '0');
  }
  if (ms < mt) {
    ms += 60;
    hs--;
  }
  ms -= mt;
  if (hs < ht) {
    hs += 24;
  }
  hs -= ht;
  if (hs == 0)
    cout << "00";
  else if (hs < 10)
    cout << "0" << hs;
  else
    cout << hs;
  cout << ":";
  if (ms == 0)
    cout << "00";
  else if (ms < 10)
    cout << "0" << ms;
  else
    cout << ms;
  return 0;
}
