import Text.Printf

solve' :: Double->Double->Double
solve' q xn
    | (abs (xn**3.0-q)) < 0.00001*q = xn
    | otherwise                     = solve' q xn'
        where xn' = xn - (xn**3.0-q)/(3.0*xn**2.0)

solve str = do
    let q = read str :: Double
    if q==(-1) then return() else printf "%.6f\n" (solve' q (q/2.0))

main = do
    str <- getContents
    mapM_ solve $ lines str
    