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:
	import java.io.BufferedWriter;
	import java.io.IOException;
	import java.io.InputStream;
	import java.io.OutputStream;
	import java.io.OutputStreamWriter;
	import java.io.PrintWriter;
	import java.io.Writer;
	import java.util.Arrays;
	import java.util.InputMismatchException;
	import java.util.*;
	import java.io.*;
	import java.math.*;
	public class Main{

	static class Pair
		{ 
			int x; 
			int y; 
			//int z;
			public Pair(int x, int y) 
			{	 
				this.x = x; 
				this.y = y; 
				
			}	 
		} 
		
		static class Compare
		{ 
			static void compare(Pair arr[], int n) 
			{ 
				// Comparator to sort the pair according to second element 
				Arrays.sort(arr, new Comparator<Pair>() { 
					@Override public int compare(Pair p1, Pair p2) 
					{ 
						return p1.x - p2.x; 
					} 
				}); 
			} 
		}
		static class The_Comparator implements Comparator<Integer>
		{		
			public int compare(Integer str1, Integer str2) 
			{ 
				if(str2>str1)
				{
					return 1;
				}
				else if(str2==str1)
				{
					return 0;
				}
				else
				{
					return -1;
				}
			}	 
		} 
		public static long pow(long a, long b)
		{
			long result=1;
			while(b>0)
			{
				if (b % 2 != 0)
				{
					result=(result*a)%(mod);
					b--;
				} 
				a=(a*a)%(mod);
				b /= 2;
			}   
			return result;
		}
		public static long fact(long num)
		{
					long value=1;
					int i=0;
					for(i=2;i<num;i++)
					{
						value=((value%mod)*i%mod)%mod;
					}
					return value;
				}
				public static long gcd(long a, long b)
				{
					if (a == 0)
						return b;
					return gcd(b%a, a);
				}
				
				public static long lcm(int a,int b)
				{
					return a * (b / gcd(a, b));
				}
				public static long sum(int h)
				{
					return (h*(h+1)/2);
				}
				public static void dfs(int parent,boolean[] visited)
				{
					ArrayList<Integer> arr=new ArrayList<Integer>();
					arr=graph.get(parent);
					min=Math.min(min,price[parent]);
					visited[parent]=true;
					for(int i=0;i<arr.size();i++)
					{
						int num=arr.get(i);
						if(visited[num]==false)
						{
							dfs(num,visited);
						}
					}
				}
			//	static int[] count;
				static int f=0;
				static char[] ch;
				static long mod=998244353L;
				static ArrayList<ArrayList<Integer>> graph;
				static int min=100001;
				static int[] price;
				
				
				
				public static void main(String args[])throws IOException
				{
			//		InputReader in=new InputReader(System.in);
		//			OutputWriter out=new OutputWriter(System.out);
				//	long a=pow(26,1000000005);
				    BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
				//	ArrayList<Integer> ar=new ArrayList<>();
				//	ArrayList<Integer> ar1=new ArrayList<>();
				//	ArrayList<Integer> ar2=new ArrayList<>();
				//	ArrayList<Integer> ar3=new ArrayList<>();
				//	ArrayList<Integer> ar4=new ArrayList<>();
				//	TreeSet<Integer> ts=new TreeSet<>();
				//	TreeSet<Integer> ts1=new TreeSet<>();
				//	TreeSet<String> pre=new TreeSet<>();
				//	HashMap<Integer,Integer> hash=new HashMap<>();
			//		HashMap<Long,Integer> hash1=new HashMap<Long,Integer>();
			//		HashMap<Long,Integer> hash2=new HashMap<Long,Integer>();
			/*		boolean[] prime=new boolean[1000001];
					int[] count=new int[1000001];
					for(int i=2;i<=1000000;i++)
					{
						if(prime[i]==false)
						{
							count[i]++;
							for(int j=2*i;j<=1000000;j+=i)
							{
								prime[j]=true;
								count[j]++;
							}
						}
					}*/
					int n=i();
					int r=i();
					double angle=180/(double)n;
					double deg=Math.toRadians(angle);
					double sinv=Math.sin(deg);
					if(sinv<0)
					{
						sinv=-sinv;
					}
					double ans=sinv*(double)r;
					ans=ans/(1-sinv);
					pln(ans+"");
				}
	
				
				
				
				
					
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				/**/
				static InputReader in=new InputReader(System.in);
					static OutputWriter out=new OutputWriter(System.out);
					public static long l()
					{
						String s=in.String();
						return Long.parseLong(s);
					}
					public static void pln(String value)
					{
						System.out.println(value);
					}
					public static int i()
					{
						return in.Int();
					}
					public static String s()
					{
						return in.String();
					}
		}
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			 
			class InputReader {
				 
				private InputStream stream;
				private byte[] buf = new byte[1024];
				private int curChar;
				private int numChars;
				private SpaceCharFilter filter;
			 
				public InputReader(InputStream stream) {
					this.stream = stream;
				}
			 
				public int read() {
					if (numChars== -1)
						throw new InputMismatchException();
					if (curChar >= numChars) {
						curChar = 0;
						try {
							numChars = stream.read(buf);
						} catch (IOException e) {
							throw new InputMismatchException();
						}
						if (numChars <= 0)
							return -1;
					}
					return buf[curChar++];
				}
			 
				public int Int() {
					int c = read();
					while (isSpaceChar(c))
						c = read();
					int sgn = 1;
					if (c == '-') {
						sgn = -1;
						c = read();
					}
					int res = 0;
					do {
						if (c < '0' || c > '9')
							throw new InputMismatchException();
						res *= 10;
						res += c - '0';
						c = read();
					} while (!isSpaceChar(c));
					return res * sgn;
				}
			 
				public String String() {
					int c = read();
					while (isSpaceChar(c))
						c = read();
					StringBuilder res = new StringBuilder();
					do {
						res.appendCodePoint(c);
						c = read();
					} while (!isSpaceChar(c));
					return res.toString();
				}
			 
				public boolean isSpaceChar(int c) {
					if (filter != null)
						return filter.isSpaceChar(c);
					return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
				}
			 
				public String next() {
					return String();
				}
			 
				public interface SpaceCharFilter {
					public boolean isSpaceChar(int ch);
				}
			}
			 
			class OutputWriter {
				private final PrintWriter writer;
			 
				public OutputWriter(OutputStream outputStream) {
					writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
				}
			 
				public OutputWriter(Writer writer) {
					this.writer = new PrintWriter(writer);
				}
			 
				public void print(Object...objects) {
					for (int i = 0; i < objects.length; i++) {
						if (i != 0)
							writer.print(' ');
						writer.print(objects[i]);
					}
				}
			 
				public void printLine(Object...objects) {
					print(objects);
					writer.println();
				}
			 
				public void close() {
					writer.close();
				}
			 
				public void flush() {
					writer.flush();
				}
			 
				}
			 
				class IOUtils {
			 
				public static int[] readIntArray(InputReader in, int size) {
					int[] array = new int[size];
					for (int i = 0; i < size; i++)
						array[i] = in.Int();
					return array;
				}
			 
				}