#include <iostream>
#include <cstdio>
#include <vector>
#include <list>
#include <algorithm>
#include <cmath>
#include <stack>
#include <map>
#include <numeric>
#include <sstream>
#include <queue>
#include <iomanip>
using namespace std;

#define REP(i,n) for(int (i)=0; (i)<(n); (i)++)
#define FOR(i,a,b) for(int (i)=(a); (i)<(b); (i)++)
#define PUSH(n,v) for(int i=0; i<(n); i++) {int j; cin >> j; v.push_back(j);}
#define ALL(v) v.begin(), v.end()
#define print(s) cout << (s) << endl

double q;

double iter(double x) {
    return x - (x*x*x-q)/(3*x*x);
}

int main() {
    while(cin >> q, q+1) {
        double x = q/2;
        while (abs(x*x*x - q) >= 0.00001*q) {
            x = iter(x);
        }
        printf("%.6f\n", x);
    }
    return 0;
}