#include <cmath>
#include <iomanip>
#include <iostream>

using namespace std;

int main()
{
  int a;

  while(cin >> a)
  {
    if(a == -1) { goto Exit; }

    cout << setprecision(15) << pow(a, 1.0 / 3.0) << endl;
  }

Exit:;

  return 0;
}