import java.util.*; import java.io.*; public class Main { public static void main(String[] args) throws Exception { FastScanner sc = new FastScanner(System.in); PrintWriter pw = new PrintWriter(System.out); int n = sc.nextInt(); int m = sc.nextInt(); long[][] dp = new long[n+1][n+1]; for(int i = 0; i < n; i++){ Arrays.fill(dp[i],-Long.MAX_VALUE/2); } dp[0][0] = 0; for(int i = 0; i < n; i++){ int total = 0; for(int j = 0; j < m; j++){ total += sc.nextInt(); } for(int j = 0; j <= i; j++){ dp[i+1][j] = Math.max(dp[i+1][j],dp[i][j]); if(j % 2 == 0){ dp[i+1][j+1] = Math.max(dp[i+1][j+1],dp[i][j] + total); }else{ dp[i+1][j+1] = Math.max(dp[i+1][j+1],dp[i][j] - total); } } } long ans = 0; for(int i = 0; i <= n; i++){ ans = Math.max(ans,dp[n][i]); } pw.println(ans); pw.flush(); } static class GeekInteger { public static void save_sort(int[] array) { shuffle(array); Arrays.sort(array); } public static int[] shuffle(int[] array) { int n = array.length; Random random = new Random(); for (int i = 0, j; i < n; i++) { j = i + random.nextInt(n - i); int randomElement = array[j]; array[j] = array[i]; array[i] = randomElement; } return array; } } } class FastScanner { private BufferedReader reader = null; private StringTokenizer tokenizer = null; public FastScanner(InputStream in) { reader = new BufferedReader(new InputStreamReader(in)); tokenizer = null; } public String next() { if (tokenizer == null || !tokenizer.hasMoreTokens()) { try { tokenizer = new StringTokenizer(reader.readLine()); } catch (IOException e) { throw new RuntimeException(e); } } return tokenizer.nextToken(); } public String nextLine() { if (tokenizer == null || !tokenizer.hasMoreTokens()) { try { return reader.readLine(); } catch (IOException e) { throw new RuntimeException(e); } } return tokenizer.nextToken("\n"); } public long nextLong() { return Long.parseLong(next()); } public int nextInt() { return Integer.parseInt(next()); } public double nextDouble() { return Double.parseDouble(next()); } public String[] nextArray(int n) { String[] a = new String[n]; for (int i = 0; i < n; i++) a[i] = next(); return a; } public int[] nextIntArray(int n) { int[] a = new int[n]; for (int i = 0; i < n; i++) a[i] = nextInt(); return a; } public long[] nextLongArray(int n) { long[] a = new long[n]; for (int i = 0; i < n; i++) a[i] = nextLong(); return a; } }