import java.util.Scanner;

public class TimeSpan {

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

        String[] startTime = input.nextLine().split(":");
        String[] endTime = input.nextLine().split(":");

        int startHours = Integer.parseInt(startTime[0]);
        int startMinutes = Integer.parseInt(startTime[1]);
        int startSeconds = Integer.parseInt(startTime[2]);

        int endHours = Integer.parseInt(endTime[0]);
        int endMinutes = Integer.parseInt(endTime[1]);
        int endSeconds = Integer.parseInt(endTime[2]);

        int outputHours = 0;
        int outputMinutes = 0;
        int outputSeconds = 0;

        outputSeconds = startSeconds - endSeconds;
        outputMinutes = startMinutes - endMinutes;
        outputHours = startHours - endHours;

        if (outputSeconds < 0) {
            outputSeconds += 60;
            outputMinutes--;
        }
        if (outputMinutes < 0) {
            outputMinutes += 60;
            outputHours--;
        }

        System.out
                .printf("%d:%02d:%02d", outputHours, outputMinutes, outputSeconds);

    }

}