using System;

public class Program

{

    public static void Main()

    {

        int x;

        x=int.Parse(Console.ReadLine());

        if(x<11)

            Console.WriteLine(x*4.3);

        if(x>10 && x<50)

            Console.WriteLine(10*4.3+(x-10)*7);

        if(x>50)

             Console.WriteLine(10*4.3+(x-10)*7 + 0.33*(10*4.3+(x-10)*7));

    }

}