{-# LANGUAGE BangPatterns #-}
import Control.Monad
import qualified Data.ByteString.Char8 as BS
import Data.Char
import Data.List
import Data.Maybe

readInt = fst . fromJust . BS.readInteger
readIntList = map readInt . BS.words
getInt = readInt <$> BS.getLine
getIntList = readIntList <$> BS.getLine

solve :: [Integer] -> Int -> Integer
solve !s !n =
  uncurry max $
    foldl'
      (\(!a, !b) !c -> (max (b - c) a, max (a + c) b))
      (0, 0)
      s

main = do
  [n, m] <- unfoldr (BS.readInt . BS.dropWhile isSpace) <$> BS.getLine
  a <- replicateM n $ sum <$> getIntList
  print $ solve a n