{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE BangPatterns #-}

import Control.Applicative
import Control.Monad
import Control.Arrow
import Data.List
import Data.Maybe
import Data.Char
import qualified Data.ByteString.Char8 as B
import Text.Printf
import Debug.Trace

readInt = ( readLn :: IO Int )
readInts = map ( fst . fromJust . B.readInt ) . B.words <$> B.getLine

which a b f = if f then a else b
mp [ a, b ] = ( a, b )

main = do
	[ n, k ] <- readInts
	ps <- uncurry zip . ( id &&& drop ( k - 1 ) ) <$> readInts
	print $ minimum $ map solve ps

solve ( l, r )
	| r < 0 = -l
	| 0 < l = r
	| otherwise = min (-l) r + ( r - l )