九度oj1166

#include<stdio.h>
int main(){
	double x,y;
	int i,n;
	while (scanf("%lf%d", &x, &n) != EOF){
		y = x;
		i = 0;
		while (i<n){
			y = 2 * y / 3 + x / (3 * y*y);
			i++;
		}
		
		printf("%.6f\n", y);
	}
	return 0;
}