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.*;
import java.math.*;

public class C {

	public static void main(String[] args) throws Exception {
		Reader file = new Reader();

		double n = file.nextInt();
		double r = file.nextInt();

		double s = Math.sin(((2 * Math.PI) / n) / 2)
				/ (1 - Math.sin(((2 * Math.PI) / n) / 2)) * r;

		System.out.println(s);
	}

	static class Reader {
		private int BUFFER_SIZE = 1 << 16;
		private char nullChar = (char) 0;
		private byte[] buf = new byte[BUFFER_SIZE];
		private int bufferPointer = 0, bytesRead = 0;
		private char c = nullChar;
		private double num = 1;
		private InputStream in;
		private char delimeter = ' ';

		public Reader() {
			in = new BufferedInputStream(System.in, BUFFER_SIZE);
		}

		public Reader(String s) throws FileNotFoundException {
			try {
				in = new BufferedInputStream(new FileInputStream(new File(s)),
						BUFFER_SIZE);
			} catch (FileNotFoundException e) {
				throw new FileNotFoundException();
			}
		}

		public char nextChar() {
			while (bufferPointer == bytesRead) {
				try {
					bytesRead = in.read(buf);
				} catch (Exception e) {
					return nullChar;
				}
				if (bytesRead == -1)
					return nullChar;
				bufferPointer = 0;
			}
			try {
				return (char) buf[bufferPointer++];
			} catch (ArrayIndexOutOfBoundsException e) {
				throw new InputMismatchException();
			}

		}

		public int nextInt() {
			return (int) nextLong();
		}

		public long nextLong() {
			num = 1;
			boolean neg = false;
			if (c == nullChar)
				c = nextChar();
			for (; (c < '0' || c > '9'); c = nextChar()) {
				if (c == '-')
					neg = true;
			}
			long res = 0;
			for (; c >= '0' && c <= '9'; c = nextChar()) {
				res = (res << 3) + (res << 1) + c - '0';
				num *= 10;
			}
			return neg ? -res : res;
		}

		public double nextDouble() {
			double cur = nextLong();
			return c != '.' ? cur : cur + nextLong() / num;
		}

		public BigInteger nextBigInteger() {
			if (c == nullChar)
				c = nextChar();
			if (!Character.isDigit(c) && c != '-') { throw new InputMismatchException(); }
			StringBuilder strNum = new StringBuilder();
			while (Character.isDigit(c) || c == '-') {
				strNum.append(c);
				c = nextChar();
			}
			return new BigInteger(strNum.toString());
		}

		public BigDecimal nextBigDecimal() {
			if (c == nullChar)
				c = nextChar();
			if (!Character.isDigit(c) && c != '-' && c != '.') {
				throw new InputMismatchException();
			}
			StringBuilder strNum = new StringBuilder();
			while (Character.isDigit(c) || c == '-' || c == '.') {
				strNum.append(c);
				c = nextChar();
			}
			return new BigDecimal(strNum.toString());
		}

		public String next() {
			c = nextChar();
			while (c <= 32 || c == delimeter)
				c = nextChar();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = nextChar();
			} while (c > 32 || c == delimeter);
			return res.toString();
		}

		public String nextLine() {
			c = nextChar();
			while (c < 32)
				c = nextChar();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = nextChar();
			} while (c >= 32);
			return res.toString();
		}

		public char delimeter() {
			return delimeter;
		}

		public void useDelimeter(char c) {
			delimeter = c;
		}

		public boolean hasNext() {
			if (c >= 32 && c != delimeter)
				return true;
			while (true) {
				c = nextChar();
				if (c == nullChar)
					return false;
				else if (c > 32)
					return true;
			}
		}

	}
}