import java.util.Scanner;


public class exam_Problems_ALl_In_ONE {

    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);

        int minutesTotal = 0;

        while (true) {
            String inputData = input.nextLine();

            // ti si napisala tova :  input.nextLine().equals("End")
            // i po tozi na4in prospuska6e edin red a trqbva da proverqvash vhoda input data dali e "End"
            if (inputData.equals("End")) {
                break;
            }

        //String duration = inputData.replace("End", "");

            String[] hoursMinutes = inputData.split(":");

            for (int i = 0; i < hoursMinutes.length - 1; i++) {

                // tuk be6e propusnala edin + i trqbva da umnojavash po 60 za da vzeme6 minutite
                minutesTotal +=  Integer.parseInt(hoursMinutes[i]) * 60;
                minutesTotal +=  Integer.parseInt(hoursMinutes[i+1]);
            }
        }
        System.out.printf("%d:%02d", minutesTotal / 60, minutesTotal % 60);
    }

}