package main

import (
    "fmt"
    "math"
)

func CubeRoot(x float64) float64 {
    const eps = 1e-8
    sign := 1
    if x < 0 {
        x = math.Abs(x)
        sign = -1
    }

    low, high := 0.0, math.Max(1.0, x)
    for math.Abs(low - high) > eps {
        mid := (low + high) / 2
        if (math.Pow(mid, 3) - x) > eps {
            high = mid
        } else {
            low = mid
        }
    }

    return float64(sign) * low
}

func main() {
    var num float64
    fmt.Scanf("%f", &num)

    fmt.Printf("%.6f\n", CubeRoot(num))
}