import std;

void main () {
    int H, W; readln.read(H, W);
    int[][] A = new int[][](H, W);
    foreach (i; 0..H) A[i] = readln.split.to!(int[]);

    solve(H, W, A);
}

void solve (int H, int W, int[][] A) {
    /**
     *  vertical   horizontally   DUR   DLR
     *     |        ------->      _    \
     *     |                      /\   _\/
     *     v                     / 
     *
     *  0 1 2      0          0       3 2 1 0
     *             1          1       4
     *             2          2       5
     *                        3 4 5
     *
     */

    int[] vertical = new int[](W);
    int[] horizontally = new int[](H);
    int[] DLR = new int[](H+W-1);
    int[] DUR = new int[](H+W-1);

    foreach (j; 0..W) foreach (i; 0..H) vertical[j] += A[i][j];
    foreach (i; 0..H) foreach (j; 0..W) horizontally[i] += A[i][j];

    bool isInGrid (int y, int x) {
        return 0 <= y && y < H && 0 <= x && x < W;
    }

    { /* DLRの計算 */
        int idx = 0;
        int y = 0, x = W-1;
        int dy = 1, dx = 1;
        for (; 0 < x; x--) {
            int k = 0;
            while (isInGrid(y+k*dy, x+k*dx)) {
                DLR[idx] += A[y+k*dy][x+k*dx];
                k++;
            }
            idx++;
        }
        for (; y < H; y++) {
            int k = 0;
            while (isInGrid(y+k*dy, x+k*dx)) {
                DLR[idx] += A[y+k*dy][x+k*dx];
                k++;
            }
            idx++;
        }
    }
    { /* DURの計算 */
        int idx = 0;
        int y = 0, x = 0;
        int dy = -1, dx = 1;
        for (; y < H-1; y++) {
            int k = 0;
            while (isInGrid(y+k*dy, x+k*dx)) {
                DUR[idx] += A[y+k*dy][x+k*dx];
                k++;
            }
            idx++;
        }
        for (; x < W; x++) {
            int k = 0;
            while (isInGrid(y+k*dy, x+k*dx)) {
                DUR[idx] += A[y+k*dy][x+k*dx];
                k++;
            }
            idx++;
        }
    }

    /* 累積和計算はできた。。
    writeln(vertical);
    writeln(horizontally);
    writeln(DLR);
    writeln(DUR);
    */

    long ans = -long.max;

    /* 同じやつ2つ */
    if (1 < vertical.length) ans = max(ans, vertical.dup.sort!"a>b"[0..2].sum);
    if (1 == vertical.length) ans = max(ans, vertical.fold!max);

    if (1 < horizontally.length) ans = max(ans, horizontally.dup.sort!"a>b"[0..2].sum);
    if (1 == horizontally.length) ans = max(ans, horizontally.fold!max);

    if (1 < DUR.length) ans = max(ans, DUR.dup.sort!"a>b"[0..2].sum);
    if (1 == DUR.length) ans = max(ans, DUR.fold!max);

    if (1 < DLR.length) ans = max(ans, DLR.dup.sort!"a>b"[0..2].sum);
    if (1 == DLR.length) ans = max(ans, DLR.fold!max);

    /* 違うやつ2つ */
    /* 1. vertical and horizontally */
    foreach (i; 0..W) foreach (j; 0..H) ans = max(ans, vertical[i]+horizontally[j] - A[j][i]);

    /* 2. vertical and DUR */
    foreach (i; 0..W) foreach (j; 0..H+W-1) {
        if (isInGrid(j-i, i)) {
            ans = max(ans, vertical[i]+DUR[j] - A[j-i][i]);
        } else {
            ans = max(ans, vertical[i] + DUR[j]);
        }
    }

    /* 3. vertical and DLR */
    foreach (i; 0..W) foreach (j; 0..H+W-1) {
        if (isInGrid(1-W+i+j, i)) {
            ans = max(ans, vertical[i]+DLR[j] - A[1-W+i+j][i]);
        } else {
            ans = max(ans, vertical[i]+DLR[j]);
        }
    }


    /* 4. horizontally + DUR */
    foreach (i; 0..H) foreach (j; 0..H+W-1) {
        if (isInGrid(i, j-i)) {
            ans = max(ans, horizontally[i]+DUR[j] - A[i][j-i]);
        } else {
            ans = max(ans, horizontally[i]+DUR[j]);
        }
    }

    /* 5. horizontally + DLR */
    foreach (i; 0..H) foreach (j; 0..H+W-1) {
        if (isInGrid(i, W-1+i-j)) {
            ans = max(ans, horizontally[i]+DLR[j] - A[i][W-1+i-j]);
        } else {
            ans = max(ans, horizontally[i]+DLR[j]);
        }
    }

    /* 6. DUR and DLR */
    foreach (i; 0..H+W-1) foreach (j; 0..H+W-1) {
        if ((W-1+j-i)%2 == 0 && isInGrid(j-(W-1+j-i)/2, (W-1+j-i)/2)) {
            ans = max(ans, DLR[i]+DUR[j] - A[j-(W-1+j-i)/2][(W-1+j-i)/2]);
        } else {
            ans = max(ans, DLR[i]+DUR[j]);
        }
    }

    writeln(ans);
}

void read(T...)(string S, ref T args) {
    auto buf = S.split;
    foreach (i, ref arg; args) {
        arg = buf[i].to!(typeof(arg));
    }
}