#include <iostream>
using namespace std;
const double eps = 1e-8;
int main()
{
double n;
cin >> n;
double l = -10000, r = 10000;
while (abs(r - l) > eps)
{
double mid = (l + r) / 2;
if (mid * mid *mid <= n) l = mid;
else r = mid;
}
printf("%.6lf\n", l);
}