import java.io.*;
import java.util.Arrays;
import java.util.StringJoiner;
import java.util.StringTokenizer;
import java.util.function.Function;

public class Main {

    static int H, W;
    static int[][] C;

    public static void main(String[] args) {
        FastScanner sc = new FastScanner(System.in);
        H = sc.nextInt();
        W = sc.nextInt();
        C = new int[H][];
        for (int h = 0; h < H; h++) {
            C[h] = sc.nextIntArray(W);
        }

        System.out.println(solve());
    }

    static int solve() {
        // turn, Aのいる場所(w), Bのいる場所(w)
        int[][][] dp = new int[H+W-1][W][W];
        dp[0][0][0] = C[0][0];

        for (int turn = 1; turn < H+W-1; turn++) {
            for (int aw = 0; aw < W; aw++) {
                // w + h = turn
                int ah = turn - aw;
                if( ah < 0 || H <= ah ) continue;

                for (int bw = 0; bw < W; bw++) {
                    int bh = turn - bw;
                    if( bh < 0 || H <= bh ) continue;

                    int v = max(value(dp, turn-1, aw, bw), value(dp, turn-1, aw-1, bw), value(dp, turn-1, aw, bw-1), value(dp, turn-1, aw-1, bw-1));
                    if( aw != bw ) {
                        v += C[ah][aw] + C[bh][bw];
                    } else {
                        v += C[ah][aw];
                    }
                    dp[turn][aw][bw] = v;
                    // debug(turn, ah, aw, bh, bw, v);
                }
            }
        }
        return dp[H+W-2][W-1][W-1];
    }

    static int value(int[][][] dp, int turn, int aw, int bw) {
        if( 0 <= aw && aw < W && 0 <= bw && bw < W ) {
            return dp[turn][aw][bw];
        } else {
            return 0;
        }
    }

    @SuppressWarnings("unused")
    static class FastScanner {
        private BufferedReader reader;
        private StringTokenizer tokenizer;

        FastScanner(InputStream in) {
            reader = new BufferedReader(new InputStreamReader(in));
            tokenizer = null;
        }

        String next() {
            if (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        String nextLine() {
            if (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    return reader.readLine();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken("\n");
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        int[] nextIntArray(int n) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++)
                a[i] = nextInt();
            return a;
        }

        int[] nextIntArray(int n, int delta) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++)
                a[i] = nextInt() + delta;
            return a;
        }

        long[] nextLongArray(int n) {
            long[] a = new long[n];
            for (int i = 0; i < n; i++)
                a[i] = nextLong();
            return a;
        }
    }

    static <A> void writeLines(A[] as, Function<A, String> f) {
        PrintWriter pw = new PrintWriter(System.out);
        for (A a : as) {
            pw.println(f.apply(a));
        }
        pw.flush();
    }

    static void writeLines(int[] as) {
        PrintWriter pw = new PrintWriter(System.out);
        for (int a : as) pw.println(a);
        pw.flush();
    }

    static void writeLines(long[] as) {
        PrintWriter pw = new PrintWriter(System.out);
        for (long a : as) pw.println(a);
        pw.flush();
    }

    static int max(int... as) {
        int max = Integer.MIN_VALUE;
        for (int a : as) max = Math.max(a, max);
        return max;
    }

    static int min(int... as) {
        int min = Integer.MAX_VALUE;
        for (int a : as) min = Math.min(a, min);
        return min;
    }

    static void debug(Object... args) {
        StringJoiner j = new StringJoiner(" ");
        for (Object arg : args) {
            if (arg instanceof int[]) j.add(Arrays.toString((int[]) arg));
            else if (arg instanceof long[]) j.add(Arrays.toString((long[]) arg));
            else if (arg instanceof double[]) j.add(Arrays.toString((double[]) arg));
            else if (arg instanceof Object[]) j.add(Arrays.toString((Object[]) arg));
            else j.add(arg.toString());
        }
        System.err.println(j.toString());
    }
}
