#include<iostream>
#include<cstdio>
#include<vector>
#include<queue>
#include<algorithm>
#include<cmath>
#include<string>
#include<cstring>
#include<map>
#include<functional>
#include<stack>
#include<list>
#include<set>
#include<deque>
#include<climits>
using namespace std;

double abso(double n){
	if(n<0) return n*=-1;
	return n;
}

int main(){
	double q,x;
	cin>>q;
	x = q/2;
	while(abso(x*x*x-q)>=0.00001*q){
		x = x-((x*x*x-q)/(3*x*x));
	}
	printf("%lf\n",x);
	return 0;
}