#include <bits/stdc++.h>
using namespace std;
vector<long long> v[200001];
stack<char> sta;
map<long long, long long> mp, pm;
set<long long> st;
set<long long>::iterator P;
long long A[200001], B[200001], n, m, t, k, i, j, sum;
string s;
long long a, b, c, d;
int main() {
  ios_base::sync_with_stdio(false), cin.tie(NULL), cout.tie(NULL);
  cin >> s;
  a = (s[0] - 48) * 10 + s[1] - 48, b = (s[3] - 48) * 10 + s[4] - 48;
  cin >> s;
  c = (s[0] - 48) * 10 + s[1] - 48, d = (s[3] - 48) * 10 + s[4] - 48;
  b < d ? c++ : 1;
  a = (a + 24 - c) % 24, b = (b + 60 - d) % 60;
  s[0] = a / 10 + 48, s[1] = (a % 10) + 48, s[3] = b / 10 + 48,
  s[4] = (b % 10) + 48;
  cout << s << endl;
  return 0;
}
