#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  string s, g;
  cin >> s >> g;
  int a1 = ((int)s[0] - '0') * 10 + ((int)s[1] - '0');
  int a2 = ((int)s[3] - '0') * 10 + ((int)s[4] - '0');
  int b1 = ((int)g[0] - '0') * 10 + ((int)g[1] - '0');
  int b2 = ((int)g[3] - '0') * 10 + ((int)g[4] - '0');
  int c1 = 0;
  int c2 = 0;
  while (!(a1 == b1 && b2 == a2)) {
    c1++;
    b2++;
    if (c1 == 60) {
      c2++;
      c1 = 0;
    }
    if (b2 == 60) {
      b1++;
      b2 = 0;
    }
    if (b1 == 24) {
      b1 = 0;
    }
  }
  string k1 = to_string(c1);
  string k2 = to_string(c2);
  if (k1.size() == 1) k1 = "0" + k1;
  if (k2.size() == 1) k2 = "0" + k2;
  cout << k2 << ':' << k1 << endl;
}
