#include <bits/stdc++.h>
using namespace std;
long long n, m, a, b, c, d;
long long cnt, mx;
char z, x;
map<int, int> mp;
int main() {
  cin >> a >> z >> b >> c >> x >> d;
  a -= c;
  b -= d;
  if (b < 0) b += 60, a--;
  if (a < 0) a += 24;
  if (a <= 9 and b <= 9) cout << "0" << a << ":0" << b;
  if (a <= 9 and b > 9) cout << "0" << a << ":" << b;
  if (a > 9 and b <= 9)
    cout << a << ":0" << b;
  else if (a > 9 and b > 9)
    cout << a << ":" << b;
}
