#include <bits/stdc++.h>
using namespace std;
int main() {
  string a;
  string b;
  cin >> a >> b;
  int cnt = 0;
  int x = 0;
  int y = 0;
  x = 10 * (a[3] - '0');
  x += (a[4] - '0');
  y = 10 * (b[3] - '0');
  y += (b[4] - '0');
  x -= y;
  if (x < 0) {
    x += 60;
    cnt++;
  }
  int X = 0, Y = 0;
  X = 10 * (a[0] - '0');
  X += (a[1] - '0');
  Y = 10 * (b[0] - '0');
  Y += (b[1] - '0' + cnt);
  X -= Y;
  if (X < 0) X = 24 + X;
  string g;
  int k = 0;
  k = X / 10;
  g += k + '0';
  g += X % 10 + '0';
  g += ':';
  k = x / 10;
  g += k + '0';
  g += x % 10 + '0';
  cout << g;
}
