#include<bits/stdc++.h>
using namespace std;
double q(double a)
{
    return a*a*a;
}
int main()
{
    double n; cin >> n;
    double l = -10000, r = 10000;
    while(r - l > 1e-7)
    {
        double mid = (l+r)/2;
        if(mid*mid*mid <= n) l = mid;
        else r = mid;
    }
    printf("%.6f",r);
}