#include<stdio.h>
#include<math.h>
int main(void)
{
	double q, x, eq;
	while(scanf("%lf",&q),q>0)
	{
		x = q/2;
		eq = q*0.00001;
		while(fabs(x*x*x-q) >= eq)
			x -= (x*x*x-q)/(3*x*x);
		printf("%f\n", x);
	}
	return 0;
}