import java.util.Scanner;

public class Test {
	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
		System.out.println("請輸入k的值（奇數）：");
		int k = input.nextInt();
		if (k % 2 == 1) {
			System.out.println("請輸入n的值（整數）：");
			int n = input.nextInt();
			System.out.println("表示式的值為" + getSum(k, n));
		} else {
			System.out.println("您輸入的不是奇數，請重新執行");
		}
	}

	public static double getSum(int k, int n) {
		double sum = 0.0;
		int num = (k + 1) / 2;
		double[] a = new double[num];
		double[] b = new double[num];
		for (int i = 0; i < num; i++) {
			if (i == 0) {
				a[i] = 1;
				b[i] = n;
			} else {
				a[i] = a[i - 1] * (2 * i) * (2 * i + 1);
				b[i] = b[i - 1] * n * n;
			}
			sum += a[i] / b[i];
		}
		return sum;
	}
}