import std.stdio, std.string, std.conv;
import std.array, std.algorithm, std.range;
import std.math;

void main()
{
    foreach(q;stdin.byLine().map!(to!real).array().until(-1))
    {
        immutable EPS = 0.00001*q;
        auto x=q/2;
        while(abs(x^^3-q)>=EPS) x-=(x^^3-q)/(3*x^^2);
        writefln("%.6f",x);
    }
}