static void Main(String[] args) {
        double p = 1.0/3.0;
        Console.WriteLine(digitScale( geometricDist(5, p), 3 ));
    }
    
    static double geometricDist(int n, double p)
    {
        return p * Math.Pow(1-p, n-1);
    }
    static double digitScale(double d, int scale ){
        double factor = Math.Pow(10, scale);
        return Math.Round(d * factor)/factor;
    }