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 JAVA):

Solution:
//package sept;

import java.io.*;
import java.util.*;

public class TimePass implements Runnable {
    InputStream is;
    PrintWriter out;
    String INPUT = "1 2";
    //boolean codechef=false;
    boolean codechef=true;
    static int mod=998244353;
    static int mod2=1000000007;
	static LinkedList<Integer>[] mult;
	static LinkedList<Integer>[] g2;
	static int[][] g;
	static int[] a;
    void solve() throws IOException
	{/*
    	int n=ni();
    	a=new int[n];
    	int N=200040;
    	mult=new LinkedList[N];
    	g2=new LinkedList[N];
    	for(int i=0;i<N;i++)
    	{
    		mult[i]=new LinkedList<>();
    		g2[i]=new LinkedList<>();
    	}
    	for(int i=0;i<n;i++)
    	{
    		a[i]=ni();
    		int x=a[i];
    		for(int j=2;(long)j*j<=a[i];j++)
    		{
    			if(a[i]%j==0)
    			{
    				mult[j].add(i);
    				while(a[i]%j==0)
    				{
    					a[i]/=j;
    				}
    			}
    		}
    		if(a[i]>1)mult[a[i]].add(i);
    		a[i]=x;
    	}
    	int[] from=new int[2*(n-1)];
    	int[] to=new int[2*(n-1)];
    	int ind=0;
    	for(int i=0;i<n-1;i++)
    	{
    		int u=ni()-1,v=ni()-1;
    		from[ind++]=u;
    		to[ind-1]=v;
    		from[ind++]=v;
    		to[ind-1]=u;
    	}
    	g=packD(n,from,to);
    	ans=0;
    	used=new int[N];
    	cc=0;
    	d=new int[N];
    	for(int p=2;p<N;p++)
    	update(p);
    	
    	out.println(ans);
    	*/
    	int n=ni(),r=ni();
    	double theta=2*Math.PI/n;
    	theta=(Math.PI-theta)/2;
    	double R=(r*Math.cos(theta))/(1-Math.cos(theta));
    	out.println(R);
	}
    
    static int ans;
    
    void update(int p)
    {
    	if(mult[p].isEmpty())return;
    	for(int x:mult[p])
    	{
    		g2[x].clear();
    		for(int y:g[x])
    		{
    			if(a[y]%p==0)
    			{
    				g2[x].add(y);
    			}
    		}
    	}
    	HashSet<Integer> used=new HashSet<>();
    	for(int x:mult[p])
    	{
    		if(!used.contains(x))
    		{
    			Pair z1=bfs(x, used);
    			Pair z2=bfs(z1.a, used);
    			ans=Math.max(ans, z2.b);
    		}
    	}
    }
    
    static int[] used;
    static int cc;
    static int[] d;
    
    
    Pair bfs(int x,HashSet<Integer> set)
    {
    	cc++;
    	Queue<Integer> q=new LinkedList<>();
    	q.offer(x);
    	d[x]=1;
    	used[x]=cc;
    	Pair ans=new Pair(x,d[x],0);
    	while(!q.isEmpty())
    	{
    		int curr=q.poll();
    		set.add(curr);
    		ans.a=curr;
    		ans.b=d[curr];
    		for(int next:g2[curr])
    		{
    			if(used[next]!=cc)
    			{
    				used[next]=cc;
    				d[next]=d[curr]+1;
    				q.offer(next);
    			}
    		}
    	}
    	return ans;
    }
    

	static long fnc(int x,int y)
    {
    	return x+(long)1000000007*y;
    }

	static int[][] packD(int n,int[] from,int[] to)
	{
		int[][] g=new int[n][];
		int[] p=new int[n];
		for(int f:from)
		{
			p[f]++;
		}
		int m=from.length;
		for(int i=0;i<n;i++)
		{
			g[i]=new int[p[i]];
		}
		for(int i=0;i<m;i++)
		{
			g[from[i]][--p[from[i]]]=to[i];
		}
		return g;
	}
	    
    static class Pair
    {
        int a,b,ind;
        public Pair(int a,int b,int ind)
        {
            this.a=a;
            this.b=b;
            this.ind=ind;
        }
    }
    
    static long lcm(int a,int b)
    {
        long val=a;
        val*=b;
        return (val/gcd(a,b));
    }
    
    static long gcd(long a,long b)
    {
        if(a==0)return b;
        return gcd(b%a,a);
    }
    
    static int pow(int a, int b, int p)
    {
        long ans = 1, base = a;
        while (b!=0)
        {
            if ((b & 1)!=0)
            {
                ans *= base;
                ans%= p;
            }
            base *= base;
            base%= p;
            b >>= 1;
        }
        return (int)ans;
    }

    static int inv(int x, int p)
    {
        return pow(x, p - 2, p);
    }
    
    public void run()
    {
        if(codechef)oj=true;
        is = oj ? System.in : new ByteArrayInputStream(INPUT.getBytes());
        out = new PrintWriter(System.out);
        
        long s = System.currentTimeMillis();
        try {
			solve();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
        out.flush();
        tr(System.currentTimeMillis()-s+"ms");
    }
    
    public static void main(String[] args) throws Exception {new Thread(null,new TimePass(),"Main",1<<26).start();}
    
    private byte[] inbuf = new byte[1024];
    public int lenbuf = 0, ptrbuf = 0;
    
    private int readByte()
    {
        if(lenbuf == -1)throw new InputMismatchException();
        if(ptrbuf >= lenbuf){
            ptrbuf = 0;
            try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); }
            if(lenbuf <= 0)return -1;
        }
        return inbuf[ptrbuf++];
    }
    
    private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); }
    private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; }
    
    private double nd() { return Double.parseDouble(ns()); }
    private char nc() { return (char)skip(); }
    
    private String ns()
    {
        int b = skip();
        StringBuilder sb = new StringBuilder();
        while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ')
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }
    
    private char[] ns(int n)
    {
        char[] buf = new char[n];
        int b = skip(), p = 0;
        while(p < n && !(isSpaceChar(b))){
            buf[p++] = (char)b;
            b = readByte();
        }
        return n == p ? buf : Arrays.copyOf(buf, p);
    }
    
    private char[][] nm(int n, int m)
    {
        char[][] map = new char[n][];
        for(int i = 0;i < n;i++)map[i] = ns(m);
        return map;
    }
    
    private int[] na(int n)
    {
        int[] a = new int[n];
        for(int i = 0;i < n;i++)a[i] = ni();
        return a;
    }
    
    private int ni()
    {
        int num = 0, b;
        boolean minus = false;
        while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
        if(b == '-'){
            minus = true;
            b = readByte();
        }
        
        while(true){
            if(b >= '0' && b <= '9'){
                num = num * 10 + (b - '0');
            }else{
                return minus ? -num : num;
            }
            b = readByte();
        }
    }
    
    private long nl()
    {
        long num = 0;
        int b;
        boolean minus = false;
        while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
        if(b == '-'){
            minus = true;
            b = readByte();
        }
        
        while(true){
            if(b >= '0' && b <= '9'){
                num = num * 10 + (b - '0');
            }else{
                return minus ? -num : num;
            }
            b = readByte();
        }
    }
    
    private boolean oj = System.getProperty("ONLINE_JUDGE") != null;
    private void tr(Object... o) { if(!oj)System.out.println(Arrays.deepToString(o)); }
}