#include<stdio.h>
double num = 27;
double f(double x){return (((x)*(x)*(x))-num);}
int main()
{
double xn,tmp,x;
for(int i=0;;i++)
xn=((tmp)-(f(tmp)/((3*(tmp)*(tmp)))));
for(int i=0;x!=xn;i++)
{
x=xn;
xn=((xn)-(f(xn)/(3*(tmp)*(tmp))));
}
printf("%f",xn);
return 0;
}