#include <bits/stdc++.h>
using namespace std;
int main() {
  int hour1, hour2, minutes1, minutes2, hour3, minutes3;
  char c;
  cin >> hour1 >> c >> minutes1 >> hour2 >> c >> minutes2;
  if (hour1 < hour2)
    hour3 = (24 + hour1) - hour2;
  else
    hour3 = hour1 - hour2;
  if (minutes1 < minutes2) {
    minutes3 = (60 + minutes1) - minutes2;
    hour3--;
  } else
    minutes3 = minutes1 - minutes2;
  if (hour3 < 0) hour3 += 24;
  if (hour3 < 10 && minutes3 < 10)
    cout << "0" << hour3 << c << "0" << minutes3 << endl;
  else if (hour3 < 10)
    cout << "0" << hour3 << c << minutes3 << endl;
  else if (minutes3 < 10)
    cout << hour3 << c << "0" << minutes3 << endl;
  else
    cout << hour3 << c << minutes3 << endl;
  return 0;
}
