import Data.List

main = do
  _ <- getLine
  d <- map read . words <$> getLine
  [x, y] <- map read . words <$> getLine
  print $ solve d x y

solve :: [Int] -> Int -> Int -> Int
solve d x y
  | x == 0 && y == 0 = 0
  | (abs x + abs y) `elem` d = 1 
  | f = 2
  | otherwise = -1
  where
    dist = x + y
    f = if even dist
          then dist <= 2 * maximum d
          else let (_, _, ans) = foldl' g (0, 0, False) (sort d) in ans
    g :: (Int, Int, Bool) -> Int -> (Int, Int, Bool)
    g (evenMax, oddMax, ans) v
      | even v    = (max evenMax v, oddMax, ans || abs (dist - x) <= evenMax)
      | otherwise = (evenMax, max oddMax v, ans || abs (dist - x) <= oddMax)