
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;

int main(){
    long long n;
    double prev=0,now=0;
    while(cin>>n){
        if(n==-1)break;
        now = n/2.0;
        while(!(abs(pow(now,3) - n ) < (0.00001 * n))){
            prev = now;
            now = prev - (pow(prev, 3) - n)/(3*pow(prev,2));
        }
        printf("%.6f\n", now);
    }
    
}
