import java.io.PrintWriter
import java.util.*
import kotlin.math.*

fun PrintWriter.solve() {
    val n = nextInt()
    val m = nextInt()
    val a = Array(n) { LongArray(m) { 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.maxOrNull())
}

fun main() {
    Thread(null, {
        val writer = PrintWriter(System.out, false)
        writer.solve()
        writer.flush()
    }, "solve", 1.shl(26)).start()
}

// region Scanner
private var st = StringTokenizer("")
private val br = System.`in`.bufferedReader()

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()
// endregion