#include <iostream>
#include <cmath>

using namespace std;

int main() {
	int n2, x;
	double s2 = 0;
	cin >> n2 >> x;;
	for (int i = 1; i <= n2; ++i) {
		s2 += 1 + (pow(-1, (i + 1)) * pow(x, (i * 2) + 1) / pow(i, 3) + pow(i, 2));
	}
	cout << s2;
	return 0;

}