using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp21
{
    class Program
    {
        static void Main(string[] args)
        {
            int age = int.Parse(Console.ReadLine());
            double cenaPeralnq = double.Parse(Console.ReadLine());
            int cenaIgrachka = int.Parse(Console.ReadLine());

            int evenRd = 0;
            int oddRd = 0;
            double money = evenRd + oddRd;

            double ostatyk = Math.Round((money - cenaPeralnq), 2);

            for (int i = 1; i <= age; i++)
            {
                if (i%2==0)
                {
                    evenRd = (i * 10) / 2 - i;
                }
                else
                {
                    oddRd = cenaIgrachka * (age / 2);
                }
            }





        }
    }
}