#include <iostream>
#include <vector>
#include <stack>
#include <queue>
#include <algorithm>
#include <string>
#include <bitset>
#include <map>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <sstream>
#include <fstream>
//#include <tuple>
#include <set>
#include <string.h>
#include <functional>

#define X first
#define Y second
#define MP make_pair
//#define MT make_tuple
#define REP(i, a, n) for(int (i) = (a); (i) < (n); ++(i))
#define FOR(i, n) REP(i, 0, n)
typedef long long ll;
using namespace std;
const int MAX = 500;

template<class T, class U>
void convert(T &t, U &u)
{
	stringstream ss;
	ss << t;
	ss >> u;
}

int main()
{
	ll q;
	while( cin >> q ){
		if( q == -1 ) break;
		double x = q / 2;
		while(  abs( x * x * x - q ) >= 0.000010 * q){
			x = x - (x * x * x - q) / ( 3 * x * x );
		}
		printf("%.06f\n", x);
	}
	return 0;
}