import Data.List

solve xs
    | any (== 0) xs'        = "NO"
    | all (== head xs') xs' = "YES"
    | otherwise             = "NO"
    where
        xs' = zipWith (-) (tail xs) (init xs)

main = do
    getLine
    xs <- sort . map read . words <$> getLine
    putStrLn $ solve xs