incline :: Double -> Double -> Double -> Double
incline a b x = let c = x * 2 / a / b in
                if c < a
                then b / c
                else let h = (b - x / a / a) * 2 in h / a

main = do
  a:b:x:_ <- map read . words <$> getLine :: IO [Integer]
  putStrLn $ show $ (\x -> atan x * 180 / pi) $ incline (fromIntegral a) (fromIntegral b) (fromIntegral x)
