Time +15 min

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

namespace _14.Time_Plus_15_Minutes
{
    class TimePlus15Minutes
    {
        static void Main(string[] args)
        {
            int hour = int.Parse(Console.ReadLine());
            int minutes = int.Parse(Console.ReadLine());

            int addMinutes = minutes + 15;

            if (addMinutes>59)
            {
                hour++;
                addMinutes -= 60;

                if (hour > 23)
                {
                    hour = 0;
                }

                Console.WriteLine("{0}:{1:00}", hour, addMinutes);
            }
            else
            {
                Console.WriteLine("{0}:{1:00}",hour,addMinutes);
            }
        }
    }
}