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

main :: IO ()
main = do
  [n, m] <- readil B.readInt <$> B.getLine
  solve n <$> replicateM m (readi B.readInt <$> B.getLine) >>= print

solve :: Int -> [Int] -> Int
solve n = minimum . (drop (n-1) >>= zipWith f) . sort
  where f i j | i * j >= 0 = max (abs i) (abs j)
              | otherwise = (abs i) + (abs j) + min (abs i) (abs j)

readi :: Integral a =>  (ByteString -> Maybe (a, ByteString)) -> ByteString -> a
readi f s = let Just (n, _) = f s in n

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