class Dynamic{
    public static double eval(int n){
        double [] c = new double [n+1];
        c[0] = 1.0; 
        for (int i = 1; i <= n; i++){
            double sum = 0.0;
            for (int j = 0; j < i; j++){
                sum = sum + c[j];
            }
            c[i] = 2.0 * sum/i + i;
        }
        return c[n];
    }
}