// Arup Guha
// 3/21/2017
// Solution to 1991 UCF HS Contest Problem: Going in Circles

import java.util.*;

public class polygon {

	public static void main(String[] args) {

		Scanner stdin = new Scanner(System.in);

		// Read till eof
		while (stdin.hasNext()) {

			// Get input.
			int n = stdin.nextInt();
			double r = stdin.nextDouble();

			// Get central angle of one triangle, then add up the areas of each of the n triangles.
			double angle = 2*Math.PI/n;
			double area = n*(r*r*Math.sin(angle)/2);

			// Output result.
			System.out.printf("Area = %.2f\n", area);
		}
	}
}