prop

class Rectangle
{
    private double length;
    private double width;

    public double Length
    {
        get
        {
            return length;
        }
        set
        {
            if ( value > 0.0)
                length = value;
        }
    }

    public double Width
    {
        get
        {
            return width;
        }
        set
        {
            if (value > 0.0 )
                width = value;
        }
    }

    public double GetArea()
    {
        return length * width;
    }
}