main :: IO ()
main = do
    [a,b,x] <- map read . words <$> getLine :: IO [Double]
    let y  = 2 * x / b / a
        y' = b - ((x / a * 2 / a) - b)
    print $ if b < y
                then ((atan (y' / a)) * 180 / pi)
                else 90 - ((atan (y / b)) * 180 / pi)
