04. Clever Lily

using System;

namespace CleverLily
{
    class Program
    {
        static void Main(string[] args)
        {
            int age = int.Parse(Console.ReadLine());
            double machine = double.Parse(Console.ReadLine());
            double toyPrice = double.Parse(Console.ReadLine());
            double sum = 0;
            int toy = 0;
            int birthday = 10;

            for (int i = 1; i <= age; i++)
            {
                if (i % 2 == 0)
                {
                    sum += birthday - 1;
                    birthday += 10;
                }
                else
                {
                    toy++;
                }
            }
                sum += toy * toyPrice;

            if (sum >= machine)
            {
                Console.WriteLine($"Yes! {sum - machine:f2}");
            }
            else
            {
                Console.WriteLine($"No! {machine - sum:f2}");
            }
        }
    }
}

РЕШЕНИЕ С ТЕРНАРЕН ОПЕРАТОР:

using System;

namespace CleverLily
{
    class Program
    {
        static void Main()
        {
            int age = int.Parse(Console.ReadLine());
            double machine = double.Parse(Console.ReadLine());
            double toyPrice = double.Parse(Console.ReadLine());
            int toy = 0, birthday = 10;

            for (int i = 1; i <= age; i++)
            {
                _machine -= i % 2 == 0 ? 5 * i - 1 : toyPrice;
            }

            Console.WriteLine($"{(machine > 0 ? "No" : "Yes")}! {Math.Abs(machine):f2}");
        }
    }
}