Description

Calculate the value of the Hermite polynomial.

$$h_n(x)=\left\{ \begin{aligned} 1&,&n=0\\ 2x&,&n=1\\ 2xh_{n-1}(x)-2(n-1)h_{n-2}(x)&,& n>1 \end{aligned} \right. $$

For given $x$ and a positive integer $n$, compute the value of the polynomial.

Input Format

Input $n$ and $x$.

Output Format

Output the value of the polynomial, rounded to 2 decimal places.

1 2

4.00

Hint

$(n \le 8，x \le 8)$