#include <bits/stdc++.h>
#define REP(i,n) for(int i=0;i<n;i++)
#define LOOP(i,x,n) for(int i=x;i<n;i++)
#define ALL(v) (v).begin(),(v).end()
#define PB push_back
#define MP make_pair
#define FR first
#define SC second
#define int long long
using namespace std;
const int MOD=1000000007;
const int INF=1000000009;


signed main(){
  int n;
  while(cin>>n,n!=-1){
    double x=n/2.0;
    while(abs(pow(x,3)-n)>=0.00001*n){
      x=x-(double)(pow(x,3)-n)/(3*pow(x,2));
    }
    printf("%f\n",x);
  }
  return 0;
}

