func main()
	var n: int :: cui@inputInt()
	var m: int :: cui@inputInt()
	var a: []int :: #[n]int
	for i(0, n - 1)
		var sum: int :: 0
		for(1, m)
			do sum :+ cui@inputInt()
		end for
		do a[i] :: sum
	end for
	
	; i個目, j: それまでに食べた個数が奇数なら1
	var dp: [][]int :: #[n, 2]int
	for i(0, n - 1)
		do dp[i][0] :: -10 ^ 20
		do dp[i][1] :: -10 ^ 20
	end for
	do dp[0][0] :: 0
	do dp[0][1] :: a[0]
	
	for i(1, n - 1)
		do dp[i][0] :: [dp[i - 1][0], dp[i - 1][1] - a[i]].max()
		do dp[i][1] :: [dp[i - 1][1], dp[i - 1][0] + a[i]].max()
	end for
	var ans: int :: dp[n - 1].max()
	do cui@print("\{ans}\n")
end func