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(); } }