//x(n+1)=x(n)-f(xn)/f'(xn)
//f(x)=x^3 - Y;
#include<iostream>
using namespace std;
double f_(double x){
    return 3*x*x;
}
double f(double x,double k){
    return x*x*x-k;
}
int main(){
    double num;
    cin>>num;
    int time=100;
    double xn;
    double xn_=num;
    while(time--){
        xn=xn_ -f(xn_,num)/f_(xn_);
        xn_=xn;
    }
    printf("%.6f",xn);
}