#include <bits/stdc++.h>
int main() {
  char start[10] = {'\0'};
  char range[10] = {'\0'};
  scanf("%s", start);
  scanf("%s", range);
  int hour, minutes;
  hour = ((start[0] - 48) * 10) + (start[1] - 48);
  minutes = ((start[3] - 48) * 10) + (start[4] - 48);
  int mhour, mminutes;
  mhour = ((range[0] - 48) * 10) + (range[1] - 48);
  mminutes = ((range[3] - 48) * 10) + (range[4] - 48);
  int anshour = hour - mhour;
  int ansminutes = minutes - mminutes;
  if (anshour < 0) anshour += 24;
  if (ansminutes < 0) {
    anshour -= 1;
    if (anshour < 0) anshour += 24;
    ansminutes += 60;
  }
  char answer[10] = {'\0'};
  if (anshour < 10) {
    answer[0] = '0';
    answer[1] = 48 + anshour;
    answer[2] = ':';
  } else {
    if (anshour >= 20)
      answer[0] = '2';
    else
      answer[0] = '1';
    answer[1] = anshour % 10 + 48;
    answer[2] = ':';
  }
  if (ansminutes < 10) {
    answer[3] = '0';
    answer[4] = 48 + ansminutes;
  } else {
    if (ansminutes >= 10 && ansminutes < 20)
      answer[3] = '1';
    else if (ansminutes >= 20 && ansminutes < 30)
      answer[3] = '2';
    else if (ansminutes >= 30 && ansminutes < 40)
      answer[3] = '3';
    else if (ansminutes >= 40 && ansminutes < 50)
      answer[3] = '4';
    else if (ansminutes >= 50 && ansminutes < 60)
      answer[3] = '5';
    answer[4] = ansminutes % 10 + 48;
  }
  printf("%s", answer);
  return 0;
}
