



#include<stdio.h>
 double abs(double A){
 return A<0.0?-A:A; } 
int main()
{ 
int a;
 while(scanf("%d",&a),~a){
 double p=(double)a/2.0; 
while(1){ 
p=p-((p*p*p)-(double)a)/(3.0*p*p);
 if(abs(p*p*p-(double)a)<(double)a*0.00001)break;
 //printf("%.6lf\n",p); } printf("%.6lf\n",p);
 } 
} 



