Time + 15 minutes

using System;
   public class myclass
    {
        public static void Main(string[] args)
        {
           var hour = int.Parse(Console.ReadLine());
            var min = int.Parse(Console.ReadLine());

            var sum =((hour*60) + min +15);
            var  resulthour = sum/60;
            if (resulthour >= 24)
            {
                resulthour -= 24;
            }
            var resultmin = sum % 60;

            Console.WriteLine("{0}:{1:00}",resulthour,resultmin);
       }
   }