solve x es
    | x == 1    = e0
    | otherwise = solve (x - 1) (e0:es)
    where
        e0 = 1 + (foldr (+) 0 (take 6 es)) / 6

main = do
    x <- (read :: String -> Double) <$> getLine
    print $ solve x [0.0,0.0,0.0,0.0,0.0,0.0]