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