Problem: NN is an experienced internet user and that means he spends a lot of time on the social media. Once he found the following image on the Net, which asked him to compare the sizes of inner circles:

<image>

It turned out that the circles are equal. NN was very surprised by this fact, so he decided to create a similar picture himself.

He managed to calculate the number of outer circles n and the radius of the inner circle r. NN thinks that, using this information, you can exactly determine the radius of the outer circles R so that the inner circle touches all of the outer ones externally and each pair of neighboring outer circles also touches each other. While NN tried very hard to guess the required radius, he didn't manage to do that. 

Help NN find the required radius for building the required picture.

Input

The first and the only line of the input file contains two numbers n and r (3 ≤ n ≤ 100, 1 ≤ r ≤ 100) — the number of the outer circles and the radius of the inner circle respectively.

Output

Output a single number R — the radius of the outer circle required for building the required picture. 

Your answer will be accepted if its relative or absolute error does not exceed 10^{-6}.

Formally, if your answer is a and the jury's answer is b. Your answer is accepted if and only when (|a-b|)/(max(1, |b|)) ≤ 10^{-6}.

Examples

Input

3 1


Output

6.4641016


Input

6 1


Output

1.0000000


Input

100 100


Output

3.2429391

Solution (in PYTHON3):

Solution:
def chPathToThis(f=None):
    import os
    f = __file__ if f is None else f
    os.chdir(os.path.dirname(f))

fle = None

def input():
    global fle
    def inner():
        if fle is None:
            from sys import stdin
            for line in stdin:
                yield line
            raise EOFError
        else:
            for line in fle:
                yield line.replace('\r', '').replace('\n', '')
            raise EOFError
    o = inner()
    return next(o)

import math

class SegmentTree:
    
    def __init__(self, A):
        self.N = len(A)
        self.st = [0] * (4 * self.N) # approximate the overall size of segment tree with array N
        self.build(1, 0, self.N - 1)
        
    def left(self, idx):
        return idx * 2

    def right(self, idx):
        return idx * 2 + 1

    def build(self, idx, l, r):
        if l == r:
            self.st[idx] = A[l]
        else:
            mid = (l + r) // 2
            self.build(self.left(idx), l, mid)
            self.build(self.right(idx), mid + 1, r)
            self.st[idx] = max(self.st[self.left(idx)] , self.st[self.right(idx)])
    
    def update(self, a, b, val):
        return self.update_recursive(1, 0, self.N - 1, a - 1, b - 1, val)
    
    def update_recursive(self, idx, l, r, a, b, val): # update(1, 1, N, a, b, v) for update val v to [a,b]
        if r < a or l > b:
            return True
        if l == r :
            self.st[idx] = val
            return True
        mid = (l+r)//2
        self.update_recursive(self.left(idx), l, mid, a, b, val)
        self.update_recursive(self.right(idx), mid+1, r, a, b, val)
        self.st[idx] = max(self.st[self.left(idx)] , self.st[self.right(idx)])
        return True

    def query(self, a, b):
        return self.query_recursive(1, 0, self.N - 1, a - 1, b - 1)

    def query_recursive(self, idx, l, r, a, b): #query(1, 1, N, a, b) for query max of [a,b]
        if r < a or l > b:
            return -math.inf
        if l >= a and r <= b:
            return self.st[idx]
        mid = (l+r)//2
        q1 = self.query_recursive(self.left(idx), l, mid, a, b)
        q2 = self.query_recursive(self.right(idx), mid + 1, r, a, b)
        return max(q1, q2)

    def showData(self):
        showList = []
        for i in range(1,N+1):
            showList += [self.query(i, i)]
        print (showList)

A = []
N = 0

def main():
    tmp = input().split()
    n, r = int(tmp[0]), float(tmp[1])
    from math import cos, acos
    PI = acos(-1.0)
    aim = cos(PI * (n - 2) / (2 * n))
    left, right = 0.0, 100000000.0
    while right - left >= 1e-8:
        mid = (right + left) / 2
        if mid / (r + mid) < aim:
            left = mid
        else:
            right = mid
    print(left)



try:
    import time, numpy
    chPathToThis(__file__)
    begin, fle = time.clock(), open('pytest.txt')
    main()
    fle.close()
    print(time.clock() - begin)
except ImportError:
    main()