#include <iostream>
using namespace std;
int main()
{
double n;
cin >> n;
double l = -10000.0, r = 10000.0;
while (r - l > 1e-8) // 多保留2位
{
double m = (l + r) / 2;
if (m * m * m >= n)
r = m;
else
l = m;
}
printf("%.6lf\n", l);
return 0;
}