#include<stdio.h>
#include<math.h>
#include<iostream>
using namespace std;
double x, b = 3.0 / 2;
double fun(double x) {
    return  pow(x, b)+2*pow(x,2) - 8;
}
    int main() {
        cin >> x;
        double l = 0, r = 2;
        while (r - l >= 0.0001) {
            double mid = (l + r) / 2;
            if (fun(mid) * fun(l) < 0) r = mid;
            else if (fun(mid) * fun(r) < 0) l = mid;
        }
        cout << r<<endl;
        return 0;
    }