
import qualified Data.Vector.Unboxed as U
import qualified Data.Vector as V
import qualified Data.ByteString.Char8 as C
import qualified Data.Array.IO as A
import Debug.Trace
import Data.List
import Control.Monad
import Data.Ord

import qualified Data.IntSet as S

r :: Int -> IO (U.Vector Int)
r n = U.unfoldrN n (C.readInt . C.dropWhile (==' ')) <$> C.getLine

r' :: IO [Int]
r'  =   unfoldr    (C.readInt . C.dropWhile (==' ')) <$> C.getLine

rp :: IO (Int,Int)
rp  = toTup . unfoldr    (C.readInt . C.dropWhile (==' ')) <$> C.getLine

toTup [a,b] = (a,b)

main :: IO ()
main = do
    n <- readLn :: IO Int
    as' <- r' :: IO [Int]
    let as = U.fromList (sort as')
    (res,r) <- solve as []
    print r
    mapM_ printtup (reverse res)

printtup (x,y) = putStrLn $ unwords [show x, show y]

solve :: U.Vector Int -> [(Int,Int)] -> IO ([(Int,Int)],Int)
solve set ac
    | U.length set <= 1  = error "should not happen"
    | U.length set == 2  = let x = U.last set ; y = U.head set
                            in return ((x,y):ac, x-y)
    | otherwise = do
        let (x,rest)    = (U.last set, U.init set)
        let (y,rest')   = (U.head rest, U.tail rest)
        let (z,rest'')  = (U.head rest', U.tail rest')
        -- y < z < x
        let newset = if z < 0
            then y `U.cons` (rest'' `U.snoc` (x-z)) -- XZ
            else (y-z) `U.cons` (x `U.cons` rest'') -- YZ
        let newpair = if z < 0 then ((x,z):ac) else ((y,z):ac)

        solve newset newpair


