Time + 15 Minutes

using System;

class Program
{
    static void Main(string[] args)
    {
        int hour = int.Parse(Console.ReadLine());
        int minute = int.Parse(Console.ReadLine());
        if(minute+15>=60)
        {
            hour++;
            minute = ((minute + 15) - 60);
        }
        else
        {
            minute += 15;
        }
        if(hour>23)
        {
            hour = 0;
        }
        if(minute<10)
        {
            Console.WriteLine(hour+":0"+minute);
        }
        else
        {
        Console.WriteLine(hour+":"+minute);
        }

    }
}