#include <iostream>
#include <cstdio>
using namespace std;
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)    r = mid;
        else    l = mid;
    }
    printf("%.6lf\n", l);
    return 0;
}