#include <bits/stdc++.h>
using namespace std;
int awakeHour = 0, awakeMinute = 0, sleepHours = 0, sleepMinutes = 0;
int hourDifference, minuteDifference;
string toBedHour, toBedMinutes;
void resetTime() {
  awakeHour /= 10;
  awakeMinute /= 10;
  sleepHours /= 10;
  sleepMinutes /= 10;
}
void resolveHour(int *hd) { *hd += 24; }
void resolveMinute(int *hm) { *hm += 60; }
void redesignHour(int x) {
  if (x < 10) {
    char y = '0';
    toBedHour = "0";
    y += x;
    toBedHour += y;
  } else {
    int u, t;
    u = x % 10;
    t = x / 10;
    char y = '0' + u;
    char z = '0' + t;
    toBedHour = z;
    toBedHour += y;
  }
}
void redesignMinute(int x) {
  if (x < 10) {
    char y = '0';
    toBedMinutes = "0";
    y += x;
    toBedMinutes += y;
  } else {
    int u, t;
    u = x % 10;
    t = x / 10;
    char y = '0' + u;
    char z = '0' + t;
    toBedMinutes = z;
    toBedMinutes += y;
  }
}
void positiveMinute() {
  redesignHour(hourDifference);
  redesignMinute(minuteDifference);
  cout << toBedHour << ":" << toBedMinutes;
  exit(0);
}
void negativeMinute() {
  hourDifference--;
  if (hourDifference < 0) resolveHour(&hourDifference);
  resolveMinute(&minuteDifference);
  redesignHour(hourDifference);
  redesignMinute(minuteDifference);
  cout << toBedHour << ":" << toBedMinutes;
  exit(0);
}
int main() {
  char x;
  bool beforeColon = true;
  for (int i = 0; i < 5; ++i) {
    cin >> x;
    if (x == ':') {
      beforeColon = false;
      continue;
    }
    if (beforeColon) {
      awakeHour += x - '0';
      awakeHour *= 10;
    } else {
      awakeMinute += x - '0';
      awakeMinute *= 10;
    }
  }
  beforeColon = true;
  for (int i = 0; i < 5; ++i) {
    cin >> x;
    if (x == ':') {
      beforeColon = false;
      continue;
    }
    if (beforeColon) {
      sleepHours += x - '0';
      sleepHours *= 10;
    } else {
      sleepMinutes += x - '0';
      sleepMinutes *= 10;
    }
  }
  resetTime();
  hourDifference = awakeHour - sleepHours;
  minuteDifference = awakeMinute - sleepMinutes;
  if (hourDifference >= 0) {
    if (minuteDifference >= 0)
      positiveMinute();
    else
      negativeMinute();
  } else {
    resolveHour(&hourDifference);
    if (minuteDifference >= 0)
      positiveMinute();
    else
      negativeMinute();
  }
}
