Задача: сумиране на секунди

using System;

namespace DDDDDDDDDDDDDDDDDDDDDD
{
    class Program
    {
        static void Main(string[] args)
        {

            int firstCompetitor = int.Parse(Console.ReadLine());
            int secondCompetitor = int.Parse(Console.ReadLine());
            int threeCompetitor = int.Parse(Console.ReadLine());

            int totalSeconds = firstCompetitor + secondCompetitor + threeCompetitor;

            int minutes = totalSeconds / 60;
            int seconds = totalSeconds % 60;

            if (seconds < 10)
            {
                Console.WriteLine(minutes + ":0" + seconds);
            }
            else
            {
                Console.WriteLine((minutes + ":" + seconds));
            }


        }
    }
}