

#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);
 } 
} 



