#include <iostream>
#include <vector>
#include <string>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <algorithm>	// require sort next_permutation count __gcd reverse etc.
#include <cstdlib>	// require abs exit atof atoi 
#include <cstdio>		// require scanf printf
#include <functional>
#include <numeric>	// require accumulate
#include <cmath>		// require fabs
#include <climits>
#include <limits>
#include <cfloat>
#include <iomanip>	// require setw
#include <sstream>	// require stringstream 
#include <cstring>	// require memset
#include <cctype>		// require tolower, toupper
#include <fstream>	// require freopen
#include <ctime>		// require srand
#define rep(i,n) for(int i=0;i<(n);i++)
#define ALL(A) A.begin(), A.end()

using namespace std;

typedef long long ll;
typedef pair<int, int> P;

int main()
{
//	cut here before submit 
//	freopen ("testcase.third_root", "r", stdin );
	int q;
	while (scanf ("%d", &q ) ){
		if (q == -1 ) break;
		double x = (double)q/2.;
		do{
			x = x - (x*x*x - q)/(3.*x*x);
		}while (fabs (x*x*x - (double)q) >= 0.00001*(double)q );
		printf ("%.9lf\n", x );

	} // end loop
		
	return 0;
}