import java.io.BufferedReader
import java.io.InputStream
import java.io.InputStreamReader
import java.io.PrintWriter
import java.util.*

fun PrintWriter.solve(sc: FastScanner) {
    val n = sc.nextInt()
    val m = sc.nextInt()
    val a = Array(n) { LongArray(m) { sc.nextLong() } }
    val s = a.map { it.sum() }
    var dp = Array(n + 1) { 0L }
    for (i in 0 until n) {
        val newdp = dp
        for (j in 0 until n) {
            newdp[j + 1] = maxOf(newdp[j + 1], dp[j] + if (j % 2 == 0) s[i] else -s[i])
        }
        dp = newdp
    }
    println(dp.max())
}

fun main() {
    val writer = PrintWriter(System.out, false)
    writer.solve(FastScanner(System.`in`))
    writer.flush()
}

class FastScanner(s: InputStream) {
    private var st = StringTokenizer("")
    private val br = BufferedReader(InputStreamReader(s))

    fun next(): String {
        while (!st.hasMoreTokens()) st = StringTokenizer(br.readLine())

        return st.nextToken()
    }

    fun nextInt() = next().toInt()
    fun nextLong() = next().toLong()
    fun nextLine() = br.readLine()
    fun nextDouble() = next().toDouble()
    fun ready() = br.ready()
}