#include<bits/stdc++.h>
using namespace std;

int main(){
    double n;
    scanf("%lf", &n);
    bool flg = false;
    if (n < 0) {
        flg = true;
        n *= -1; 
    } 
    double l = 0, r = n;
    if (n < 1) r = 1;
    while(r-l > 1e-10) {
        double m = (l+r)/2;
        if (m*m*m <= n) {
            l = m;
        }else {
            r = m;
        }
    }
    if (flg) {
        printf("-");
    }
    printf("%.6lf", l);
    return 0;
}