import Data.List(sort)

main :: IO ()
main = interact $ show . solve . map read . tail . words

solve :: [Int] -> Int
solve xs
    | all (\x -> x == head xs) xs = 0
    | otherwise                   = minimum . filter (/= 0) . f . reverse . sort $ xs

f :: [Int] -> [Int]
f [x] = []
f (x:y:zs) = (x - y) : f (y:zs)