import java.util.Scanner;

public class _1_Timespan {

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String inputStart = scan.nextLine().trim();
		String inputEnd = scan.nextLine().trim();

		int[] startTimes = readInputLineAndConvertStringToIntegerNums(inputStart);
		int[] endTimes = readInputLineAndConvertStringToIntegerNums(inputEnd);

		int outSec = startTimes[2] - endTimes[2];
		if (outSec < 0) {
			startTimes[1]--;
			outSec += 60;
		}

		int outMin = startTimes[1] - endTimes[1];
		if (outMin < 0) {
			startTimes[0]--;
			outMin += 60;
		}

		int outHour = startTimes[0] - endTimes[0];

		System.out.printf("%d:%02d:%02d%n", outHour, outMin, outSec);
	}

	private static int[] readInputLineAndConvertStringToIntegerNums(
			String inputLine) {
		String[] inputs = inputLine.split(":");
		int[] nums = new int[inputs.length];
		for (int i = 0; i < nums.length; i++) {
			nums[i] = Integer.parseInt(inputs[i]);
		}

		return nums;
	}

}