class Logarithmus
{
    public static void main (String args[])
    {
        double x;
        double basis;
        double a;
        double b;

        if ( args.length == 1)
        {                                   // Ein Argument auf der Kommandozeile
            x = Double.parseDouble(args[0]);

            if (x==1)
            {
                a = 0;
            }
            else if (x==0)
            {
                System.out.println("ND");
            }
            else
            {
                a = ln(x);
                System.out.println(a);
            }
        }
        else if ( args.length == 2)
        {                                   // Zwei Argumente auf der Kommandozeile
            x = Double.parseDouble(args[0]);
            basis = Double.parseDouble(args[1]);

            if (x < 0 || basis < 0)
            {
                b = Double.NaN;
            }
            else if (x==1 || basis == 1)
            {
                b=0;
            }
            else if (x==0 || basis == 0)
            {
                System.out.println("ND");
            }
            else
            {
                b = logB(x,basis);
                System.out.println(b);
            }
        }
        else
            System.out.println(" Aufruf : Logarithmus <Wert > [<Basis >]");
    }

    public static double ln(double x)
    {
        double z;
        double sum = 0.0;

        z=(x-1)/(x+1);

        double term = z;

        for (int i = 1; sum < sum + term; i=i+2)
        {
            sum = sum + term;
            term = term*((z*z)/((i+2)/i));
        }

        sum = sum * 2;

        return sum;

    }

    public static double logB(double x, double basis)
    {
        double b;

        b = (ln(x)/ln(basis));

        return b;
    }
}
    /*/