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

using namespace std;

int main()
{
    int q;
    
    while(true)
    {
        cin >> q;
        
        if(q == -1) { break; }
        
        cout << fixed << setprecision(17) << pow(q, 1.0 / 3.0) << endl;
    }
    
    return 0;
}