#include <bits/stdc++.h>
using namespace std;
int main() {
  int q, w;
  char s[101], t[101], p[101];
  gets(s);
  gets(t);
  int h = (s[0] - '0') * 10 + s[1] - '0';
  int m = (s[3] - '0') * 10 + s[4] - '0';
  int ht = (t[0] - '0') * 10 + t[1] - '0';
  int mt = (t[3] - '0') * 10 + t[4] - '0';
  if (m >= mt)
    w = m - mt;
  else {
    m += 60;
    w = m - mt;
    h--;
  }
  if (h >= ht)
    q = h - ht;
  else {
    h += 24;
    q = h - ht;
  }
  p[0] = q / 10 + '0';
  p[1] = q % 10 + '0';
  p[2] = ':';
  p[3] = w / 10 + '0';
  p[4] = w % 10 + '0';
  p[5] = '\0';
  cout << p;
}
