#include <bits/stdc++.h>
using namespace std;
int dp[55][55][55][55];
int H, W;
int a[205][205];
int main() {
  cin >> H >> W;
  for (int i = 0; i < H; i++) {
    for (int j = 0; j < W; j++) {
      cin >> a[i][j];
    }
  }
  for (int i = 0; i < H; i++) {
    for (int j = 0; j < W; j++) {
      for (int k = 0; k < H; k++) {
        for (int l = 0; l < W; l++) {
          dp[i][j][k][l] = -INT_MAX;
        }
      }
    }
  }
  dp[0][0][0][0] = 0;
  for (int i = 0; i < H; i++) {
    for (int j = 0; j < W; j++) {
      for (int k = 0; k < H; k++) {
        for (int l = 0; l < W; l++) {
          if (i == k && j == l) {
            if (i != H - 1) {
              if (k != H - 1) {
                dp[i + 1][j][k + 1][l] =
                    max(dp[i + 1][j][k + 1][l], dp[i][j][k][l] + a[i][j]);
              }
              if (l != W - 1) {
                dp[i + 1][j][k][l + 1] =
                    max(dp[i + 1][j][k][l + 1], dp[i][j][k][l] + a[i][j]);
              }
            }
            if (j != W - 1) {
              if (k != H - 1) {
                dp[i][j + 1][k + 1][l] =
                    max(dp[i][j + 1][k + 1][l], dp[i][j][k][l] + a[i][j]);
              }
              if (l != W - 1) {
                dp[i][j + 1][k][l + 1] =
                    max(dp[i][j + 1][k][l + 1], dp[i][j][k][l] + a[i][j]);
              }
            }
          } else {
            if (i != H - 1) {
              if (k != H - 1) {
                dp[i + 1][j][k + 1][l] = max(
                    dp[i + 1][j][k + 1][l], dp[i][j][k][l] + a[i][j] + a[k][l]);
              }
              if (l != W - 1) {
                dp[i + 1][j][k][l + 1] = max(
                    dp[i + 1][j][k][l + 1], dp[i][j][k][l] + a[i][j] + a[k][l]);
              }
            }
            if (j != W - 1) {
              if (k != H - 1) {
                dp[i][j + 1][k + 1][l] = max(
                    dp[i][j + 1][k + 1][l], dp[i][j][k][l] + a[i][j] + a[k][l]);
              }
              if (l != W - 1) {
                dp[i][j + 1][k][l + 1] = max(
                    dp[i][j + 1][k][l + 1], dp[i][j][k][l] + a[i][j] + a[k][l]);
              }
            }
          }
        }
      }
    }
  }
  cout << dp[H - 1][W - 1][H - 1][W - 1] + a[H - 1][W - 1] << endl;
}
