import java.util.Scanner;


public class _01_VideoDurations {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String input = "";
		int hours =0;
		int minutes = 0;
		while (!input.equals("End")) {
			input = sc.next();
			String[] duration = input.split(":");
			int h = Integer.parseInt(duration[0]);
			int m = Integer.parseInt(duration[1]);
			hours += h + m/60;
			minutes += m%60;

		}
		System.out.println(""+hours+":"+minutes);
	}

}