{- A
f :: [Char] -> String
f (x:y:ys)
    | x == y = "Bad"
    | ys == [] ="Good"
    | otherwise = f (y:ys)

main = getLine >>= putStrLn . f
-}

del :: Int -> Int -> Int -> Int
del d x y
    | d == abs x = y
    | d == abs y = x
    | otherwise = x + y

f :: [Int] -> String
f (n:l:xs) = do
    let x = [l+i-1 | i <- [1..n] ]
    let d = minimum $ map abs x
    show $ foldr1 (del d) x

main = getLine >>= putStrLn . f . map read . words