#include <bits/stdc++.h>
using namespace std;
int main() {
  string s, s1;
  cin >> s;
  cin >> s1;
  int H = (s[0] - '0') * 10 + s[1] - '0';
  int M = (s[3] - '0') * 10 + s[4] - '0';
  int H1 = (s1[0] - '0') * 10 + s1[1] - '0';
  int M1 = (s1[3] - '0') * 10 + s1[4] - '0';
  int sm = 60 * H + M;
  int sm1 = 60 * H1 + M1;
  int ans = sm - sm1;
  int aH, aM;
  if (ans < 0) ans = 24 * 60 + ans;
  aH = ans / 60;
  aM = ans % 60;
  if (aH < 10)
    cout << '0' << aH;
  else
    cout << aH;
  cout << ':';
  if (aM < 10)
    cout << '0' << aM;
  else
    cout << aM;
}
