import java.text.ParseException;
import java.util.Scanner;


public class Timespan {

	public static void main(String[] args) throws ParseException{
		Scanner sc = new Scanner(System.in);


		String[] firstDateString = sc.nextLine().split(":");
		String[] secondDateString = sc.nextLine().split(":");



		int[] arrayFirst = new int[3];
		int[] arraySecond = new int[3];

		int[] arrayResult = new int[3];

		for (int i = 0; i < 3; i++) {
			arrayFirst[i] = Integer.parseInt(firstDateString[i]);
			arraySecond[i] = Integer.parseInt(secondDateString[i]);
		}

		int oneMindSeconds = 0;
		int oneMindMinutes = 0;

		if (arrayFirst[2] < arraySecond[2]) {
			arrayResult[2] = arrayFirst[2] + 60 - arraySecond[2];
			oneMindSeconds = 1;
		}
		else {
			arrayResult[2] = arrayFirst[2] - arraySecond[2];
		}


		if (oneMindSeconds == 1){
			if (arrayFirst[1]-1 < arraySecond[1]){
				arrayResult[1] = arrayFirst[1] - 1 + 60 - arraySecond[1];
				oneMindMinutes = 1;
			}
			else{
				arrayResult[1] = arrayFirst[1] - 1 - arraySecond[1];
			}
		}
		else{
			if (arrayFirst[1] < arraySecond[1]){
				arrayResult[1] = arrayFirst[1] + 60 - arraySecond[1];
				oneMindMinutes = 1;
			}
			else{
				arrayResult[1] = arrayFirst[1] - arraySecond[1];
			}

		}


		if (oneMindMinutes == 1) {
			arrayResult[0] = arrayFirst[0] - 1 - arraySecond[0];
		}
		else{
			arrayResult[0] = arrayFirst[0] - arraySecond[0];
		}

		if (oneMindMinutes == 1) {
			arrayResult[0] = arrayFirst[0] - 1 - arraySecond[0];
		}
		else{
			arrayResult[0] = arrayFirst[0] - arraySecond[0];
		}


		System.out.println("" + arrayResult[0] + ":" + String.format("%02d", arrayResult[1]) + ":" + String.format("%02d", arrayResult[2]));
	}


}