Sum Seconds

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication57
{
    class Program
    {
        static void Main(string[] args)
        {
            var sec1 = int.Parse(Console.ReadLine());
            var sec2 = int.Parse(Console.ReadLine());
            var sec3 = int.Parse(Console.ReadLine());
            var Totalsec = sec1 + sec2 + sec3;
            var mins=0;
            var secs=0;
            if (Totalsec >= 120)
            {
                mins = 2;
            }
            else if (Totalsec>=60)
            {
                mins = 1;
            }
            else if (Totalsec < 60)
            {
                mins = 0;
            }
            if (mins == 2)
            {
                secs = Totalsec - 120;
            }
            else if (mins==1)
            {
                secs = Totalsec-60;
            }
            else
            {
                secs = Totalsec;
            }
            if (secs < 10)
            {
                Console.WriteLine(mins + ":" + "0" + secs);
            }
            else
            {
                Console.WriteLine(mins+":"+secs);
            }
        }
    }
}