using System;

public class Program

{

    public static decimal f(decimal y, decimal z)

    {

        return 108m - (815m - 1500m / z) / y;

    }

    public static void Main()

    {

        var x0 = 4m;

        var x1 = 4.25m;

        var xi = 0m;

        for (var i = 2; i <= 30; i++)

        {

            xi = f(x1, x0);

            x0 = x1;

            x1 = xi;

        }

        Console.WriteLine(xi);

    }

}