#include <vector>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <algorithm>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <string>
#include <cstring>
#include <complex>
#include <ctime>
#include <cstdlib>

using namespace std;

inline int to_int(string s) {int v; istringstream sin(s); sin >> v; return v;}
template<class T> inline string to_str(T x) {ostringstream sout; sout << x; return sout.str();}

typedef long long ll;

int main()
{
	double x, q;
	while(cin >> q)
	{
		if(q == -1)	
			break;
		x = q / 2.0;
		while (std::abs(x*x*x-q) >= 0.00001*q)
			x -= (x*x*x - q) / (3*x*x);
		printf("%f\n", x);
	}
}