#include<iostream>
#include<algorithm>
#include<vector>
#include<stack>
#include<map>
#include<set>
#include<queue>
#include<cstdio>
#include<climits>
#include<cmath>
#include<cstring>
#include<string>
#include<sstream>
#include<complex>

#define f first
#define s second
#define mp make_pair

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define FOR(i,c) for(__typeof((c).begin()) i=(c).begin(); i!=(c).end(); i++)
#define ALL(c) (c).begin(), (c).end()

using namespace std;

typedef unsigned int uint;
typedef long long ll;
typedef complex<double> P;

#define MAX 1010

int main(){
  int q;
  while(cin>>q, q+1){
    double x = q / 2.0;
    while( abs(x*x*x - q) >= 0.00001 * q )
      x = x - (x*x*x - q) / (3*x*x);
    printf("%.6f\n",x);
  }
  return 0;
}