#include <bits/stdc++.h>
using namespace std;
int main() {
  char a[8], b[8];
  int h1, m1, h2, m2, c = 0;
  cin >> a >> b;
  h1 = (a[0] - '0') * 10 + (a[1] - '0');
  m1 = (a[3] - '0') * 10 + (a[4] - '0');
  h2 = (b[0] - '0') * 10 + (b[1] - '0');
  m2 = (b[3] - '0') * 10 + (b[4] - '0');
  if (m1 < m2) {
    m1 += 60;
    c = 1;
  }
  m2 = m1 - m2;
  if (c) h1--;
  if ((h1 < h2) || (h1 == 0 && c == 1)) h1 += 24;
  h2 = h1 - h2;
  if (h2 < 10) {
    b[0] = '0';
    b[1] = h2 + '0';
  } else {
    b[1] = '0' + h2 % 10;
    h2 /= 10;
    b[0] = h2 + '0';
  }
  b[2] = ':';
  if (m2 < 10) {
    b[3] = '0';
    b[4] = m2 + '0';
  } else {
    b[4] = '0' + m2 % 10;
    m2 /= 10;
    b[3] = m2 + '0';
  }
  cout << b << "\n";
  return 0;
}
