import Control.Applicative ((<$>))
import Data.Char (isSpace)
import Data.List (unfoldr, sort)
import Data.ByteString.Char8 (ByteString)
import qualified Data.ByteString.Char8 as B

getL :: (ByteString -> [Int]) -> IO [Int]
getL f = f <$> B.getLine

readIL :: (ByteString -> Maybe (Int, ByteString)) -> (ByteString -> [Int])
readIL f = unfoldr g
    where
        g s = do
            (n, s') <- f s
            return (n, B.dropWhile isSpace s')

main :: IO ()
main = do
    B.getLine
    putStrLn =<< solve <$> getL (readIL B.readInt)

solve :: [Int] -> String
solve xs = if any (== 0) xss then "NO" else if all (== (head xss)) xss then "YES" else "NO"
    where
        xss = f $ sort xs
        f :: [Int] -> [Int]
        f [x]      = []
        f (x:y:ys) = (y - x) : f (y:ys)