#include<iostream>
#include<string>
#include<vector>
#include<cstdio>
#include<queue>
#include<map>
using namespace std;

int main() {
	double a;
	while (scanf("%lf", &a), a + 1) {
		double b = a / 2;
		for (int c = 0; c < 100; c++) {
			if (abs(b*b*b - a) < a / 100000)break;
			double d = b*b*b - a, e = b*b * 3;
			b -= d / e;
		}
		printf("%.10lf\n", b);
	}
}