#include<iostream>
#include <math.h>
using namespace std;

int main(){
	double w;
	int d;
	int a;
	cin >> w;
	cin >> d;
	for (int i = 0; i < (d - 1); i++){
		a = w / ((d - i)*(d - i));
		w = w - a;
	}
	cout << w << endl;



	return 0;
}