3. Time + 15 Minutes

using System;

namespace Time_15Minutes
{
internal class Program
{
    static void Main(string[] args)
    {
        int myHours = int.Parse(Console.ReadLine());
        int myMinutes = int.Parse(Console.ReadLine());

        myMinutes += 15;

        if (myMinutes >= 60)
        {
            myHours += 1;
            myMinutes %= 60;
        }

        if (myHours >= 24)
        {
            myHours = 0;
        }

        if (myMinutes < 10)
        {
            Console.WriteLine($"{myHours}:0{myMinutes}");
        }
        else
        {
            Console.WriteLine($"{myHours}:{myMinutes}");
        }
    }
}
}