#include <stdio.h>

const double eps = 1e-6;

int main(){
    double x = 0;
    scanf("%lf", &x);

    double tmp = (x >= 0 ? x : -x);
    double left = 0, right = tmp;
    double mid = 0;

    while (right - left > eps){
        mid = (left + right) / 2;
        if (mid * mid * mid > tmp)
            right = mid;
        else
            left = mid;
    }

    double cubeRoot = (x >= 0 ? (left + right) / 2 : - (left + right) / 2);
    printf("%lf\n", cubeRoot);

    return 0;
}