import java.io.*;
import java.util.*;
import java.util.stream.*;

public class Main {
    static long[] values;
    static long[][] dp;
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int m = sc.nextInt();
        values = new long[n];
        for (int i = n - 1; i >= 0; i--) {
            for (int j = 0; j < m; j++) {
                values[i] += sc.nextLong();
            }
        }
        dp = new long[n][2];
        for (long[] arr : dp) {
            Arrays.fill(arr, Long.MIN_VALUE);
        }
        System.out.println(dfw(n - 1, 0));
    }
    
    static long dfw(int idx, int v) {
        if (idx < 0) {
            return 0;
        }
        if (dp[idx][v] == Long.MIN_VALUE) {
            if (v == 0) {
                dp[idx][v] = Math.max(dfw(idx - 1, v), dfw(idx - 1, 1) + values[idx]);
            } else {
                dp[idx][v] = Math.max(dfw(idx - 1, v), dfw(idx - 1, 0) - values[idx]);
            }
        }
        return dp[idx][v];
    }
} 
class Utilities {
    static String arrayToLineString(Object[] arr) {
        return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n"));
    }
    
    static String arrayToLineString(int[] arr) {
        return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new));
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public int[] nextIntArray() throws Exception {
        return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
    
}