#include<bits/stdc++.h>
using namespace std;
#define all(vec) vec.begin(),vec.end()
typedef long long int ll;
const ll MOD=1000000007;
const ll INF=1000000010;
const ll LINF=4000000000000000010LL;
const int MAX=310;
const double EPS=1e-8;
int dx[4]={0,0,1,-1};
int dy[4]={-1,1,0,0};
int main(){
	double q;
	while(cin>>q,q!=-1){
		double b=q/2;
		while(abs(pow(b,3)-q)>=0.00001*q){
			b=b-(pow(b,3)-q)/(3*pow(b,2));
		}
		printf("%.6lf\n",b);
	}
		
}

