04. Clever Lily

using System;

namespace ConsoleApp3
{
    class Program
    {
        static void Main(string[] args)
        {
            int age = int.Parse(Console.ReadLine());
            double  laundry =double.Parse(Console.ReadLine());
            int toyPrice = int.Parse(Console.ReadLine());

            double money = 0;
            for (int i = 1; i <=age; i++)
            {
                if (i % 2 == 0) //2->10(2*5) => 9 | 4->20(4*5)=> | 6->30(6*5)=>29 ...n (i*5)
                {
                    money = money + (i * 5 - 1); //money+=i*5-1;
                }
                else //1 3 6 7 ...n
                {
                    money = money + toyPrice; //money+=toyPrice
                }
            }

            if (money >= laundry)
            {
                Console.WriteLine($"Yes! {(money-laundry):F2}" );
            }
            else
            {
                Console.WriteLine($"No! {(laundry-money):F2}");
            }
        }
    }
}