import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Arrays;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] sa = br.readLine().split(" ");
		int n = Integer.parseInt(sa[0]);
		int m = Integer.parseInt(sa[1]);
		long[] a = new long[n];
		for (int i = 0; i < n; i++) {
			sa = br.readLine().split(" ");
			for (int j = 0; j < m; j++) {
				a[i] += Long.parseLong(sa[j]);
			}
		}
		br.close();

		long[][] dp = new long[2][n + 1];
		Arrays.fill(dp[0], Long.MIN_VALUE);
		Arrays.fill(dp[1], Long.MIN_VALUE);
		dp[0][0] = 0;
		dp[1][0] = 0;
		for (int i = 0; i < n; i++) {
			dp[0][i + 1] = dp[0][i];
			dp[1][i + 1] = dp[1][i];
			dp[1][i + 1] = Math.max(dp[1][i + 1], dp[0][i] + a[i]);
			dp[0][i + 1] = Math.max(dp[0][i + 1], dp[1][i] - a[i]);
		}
		System.out.println(Math.max(dp[0][n], dp[1][n]));
	}
}