#include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;
int main()
{
double n;
cin>>n;
double l=-10000;
double r=10000;
while(r-l>1e-8)
{
double mid=(r+l)/2;
if(mid*mid*mid>n)
{
r=mid;
}
else
{
l=mid;
}
}
printf("%0.6lf",l);
return 0;
}