#include<bits/stdc++.h>
#define rep(i,n)for(int i=0;i<n;i++)
using namespace std;
typedef long long ll;
typedef pair<int, int>P;

int main() {
	double q;
	while (cin >> q, q >= 0) {
		printf("%.6lf\n", cbrt(q));
	}
}