main :: IO ()
main = do
  l1 <- getLine
  let [a, b, x] = map read $ words l1 :: [Int]

  if a*a*b`div`2 > x
    then print $ 90 - 180/pi*(atan2 (fromIntegral $ 2*x) (fromIntegral $ b*a*b))
    else print $ 180/pi*(atan2 (fromIntegral $ 2*(a*a*b - x)) (fromIntegral $ a*a*a))