#include <stdio.h>
#include <math.h>
int main(void){


    int q;
      while(scanf("%d", &q)!= EOF) {
      double x;     
          
    x=q/2;
    
    
   
    if(q>0)  {
     double xx;
     
    while((fabs(x*x*x-q))>(0.00001*q)){
       
        xx=x-((x*x*x-q)/(3*x*x));
        
        x=xx;
    }
    printf("%.6f\n",xx);
      }
      }
      
}

