Untitled

import java.util.Scanner;

public class P1 {
	public static float Sol(int n, int x) {
		float s = 1 + x;

		for (int i = 1; i <= n; i++) {
			int giaithua = 1;
			for (int j = 1; j <= 2 * i; j++) {
				giaithua *= j;
			}
			s += Math.pow(x, 2 * i) / giaithua;
		}

		return s;
	}

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int x = sc.nextInt();
		int n = sc.nextInt();

		System.out.println(Sol(n, x));
	}
}