Evaluate f(x,n)

Problem Background

Special for beginners, ^_^

Problem Description

Given

$$\nf(x,n)=\sqrt{n+\sqrt{(n-1)+\sqrt{(n-2)+\sqrt{\cdots+2+\sqrt{1+x}}}}}\n$$

compute $f(x,n)$ for the given $x$ and $n$.

Input Format

Input $x$ and $n\;(1\le n \le 10)$.

Output Format

The value of the function, kept to two decimal places.

Sample Input

4.2 10

Sample Output

3.68

Constraints

1s, 1024KiB for each test case.