#include <iostream>
using namespace std;

double n;

double myCbrt(double x);

int main(){

    cin>>n;
    printf("%lf",myCbrt(n));
    return 0;
}

double myCbrt(double x){

    double l = (0 <= (x/2) ? 0:(x/2)),r = 0 <= (x/2) ? (x/2):0,mid;
    while( r - l >= 1e-7){

        mid = (l + r) / 2;
        if(mid * mid * mid > x)
            r = mid;
        else if(mid * mid * mid < x)
            l = mid;
        else
            return mid;

    }

    return mid;
}