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.*;
import java.util.*;

public class Solution {

	public static void main(String[] args) throws IOException {
		InputReader in = new InputReader(System.in);
		OutputWriter out = new OutputWriter(System.out);
//		InputReader in = new InputReader("/Users/AMANRAJ/Documents/workspace/Competitive/src/input.txt");
//		OutputWriter out = new OutputWriter("/Users/AMANRAJ/Documents/workspace/Competitive/src/output.txt");
		Task task = new Task();
		int t = 1;
		for (int i = 1; i <= t; i++) task.solve(i, in, out);
		out.close();
	}

	static class Task {
		
		public void solve(int testNumber, InputReader in, OutputWriter out) throws IOException {
			int n = in.nextInt(), r = in.nextInt();
			double alpha = Math.PI * (n - 2) / n;
			alpha = Math.cos(alpha / 2);
			double ans = r * alpha / (1 - alpha);
			out.println(ans, "\n");
 		}
	}
	
	static class InputReader {
		private BufferedReader reader;
		private StringTokenizer tokenizer;

		public InputReader(InputStream stream) {
			reader = new BufferedReader(new InputStreamReader(stream), 32768);
			tokenizer = null;
		}
		
		public InputReader(String file) throws FileNotFoundException {
			reader = new BufferedReader(new FileReader(file));
			tokenizer = null;
		}
		
		private void tokenize() {
			while (tokenizer == null || !tokenizer.hasMoreTokens()) {
				try {
					tokenizer = new StringTokenizer(reader.readLine());
				} catch (IOException e) {
					throw new RuntimeException(e);
				}
			}
		}

		public String next() {
			tokenize();
			return tokenizer.nextToken();
		}

		public int nextInt() {
			return Integer.parseInt(next());
		}

		public long nextLong() {
			return Long.parseLong(next());
		}
		
		public char nextChar() {
			return next().charAt(0);
		}
		
		public float nextFloat() {
			return Float.parseFloat(next());
		}
		
		public double nextDouble() {
			return Double.parseDouble(next());
		}

		public int[] nextIntArray(int size, int a) {
			tokenize();
			int[] arr=new int[size];
			for(int i = a; i < size; i++) {
				tokenize();
				arr[i] = Integer.parseInt(tokenizer.nextToken());
			}
			return arr;
		}
		
		public long[] nextLongArray(int size, int a) {
			tokenize();
			long[] arr=new long[size];
			for(int i = a; i < size; i++) {
				tokenize();
				arr[i] = Long.parseLong(tokenizer.nextToken());
			}
			return arr;
		}
		
		public float[] nextFloatArray(int size, int a) {
			tokenize();
			float[] arr=new float[size];
			for(int i = a; i < size; i++) {
				tokenize();
				arr[i] = Float.parseFloat(tokenizer.nextToken());
			}
			return arr;
		}

		public double[] nextDoubleArray(int size, int a) {
			tokenize();
			double[] arr=new double[size];
			for(int i = a; i < size; i++) {
				tokenize();
				arr[i] = Double.parseDouble(tokenizer.nextToken());
			}
			return arr;
		}

		public String[] nextStringArray(int size, int a) throws IOException {
			String[] arr=new String[size];
			for(int i = a; i < size; i++) 
				arr[i] = reader.readLine();
			return arr;
		}

		public char[] nextCharArray() throws IOException {
			return reader.readLine().toCharArray();
		}
	}

	static class OutputWriter {
		public PrintWriter pw;

		public OutputWriter(OutputStream stream) {
			pw = new PrintWriter(stream);
		}
		
		public OutputWriter(String file) throws IOException {
			pw = new PrintWriter(new BufferedWriter(new FileWriter(file)));
		}
		
		public void println() {
			pw.println();
		}
		
		public void println(Object... obj) {
			String delimiter = (String) obj[obj.length - 1];
			for (int i = 0 ; i < obj.length - 1; i++) pw.print(obj[i] + delimiter);
			pw.println();
		}

		public void close() {
			pw.close();
		}

		public void flush() {
			pw.flush();
		}

		public void printStringArray(String[] arr, int a, int b, String delimiter) {
			for(int i = a; i < b; i++)
				pw.println(arr[i]);
			pw.println();
		}
		
		public void printBooleanArray(boolean[] arr, int a, int b, String delimiter) {
			for(int i = a; i < b; i++)
				pw.print(arr[i] + delimiter);
			pw.println();
		}

		public void printIntArray(int[] arr, int a, int b, String delimiter) {
			for(int i = a; i < b; i++)
				pw.print(arr[i] + delimiter);
			pw.println();
		}

		public void printLongArray(long[] arr, int a, int b, String delimiter) {
			for(int i = a; i < b; i++)
				pw.print(arr[i] + delimiter);
			pw.println();
		}

		public void printCharArray(char[] arr, int a, int b, String delimiter) {
			for(int i = a; i < b; i++)
				pw.print(arr[i] + delimiter);
			pw.println();
		}

		public void printFloatArray(float[] arr, int a, int b, String delimiter) {
			for(int i = a; i < b; i++)
				pw.print(arr[i] + delimiter);
			pw.println();
		}

		public void printDoubleArray(double[] arr, int a, int b, String delimiter) {
			for(int i = a; i < b; i++)
				pw.print(arr[i] + delimiter);
			pw.println();
		}
		
		public void printIntArrayList(ArrayList<Integer> arr, int a, int b, String delimiter) {
			for(int i = a; i < b; i++)
				pw.print(arr.get(i) + delimiter);
			pw.println();
		}
		
		public void printLongArrayList(ArrayList<Long> arr, int a, int b, String delimiter) {
			for(int i = a; i < b; i++)
				pw.print(arr.get(i) + delimiter);
			pw.println();
		}
		
		public void printStringArrayList(ArrayList<String> arr, int a, int b, String delimiter) {
			for(int i = a; i < b; i++)
				pw.print(arr.get(i) + delimiter);
			pw.println();
		}
	}
}