#include <bits/stdc++.h>
using namespace std;
vector<int> dx = {1, 0, 1, 1};
vector<int> dy = {0, 1, 1, -1};
int main(){
  int H, W;
  cin >> H >> W;
  vector<vector<int>> A(H, vector<int>(W));
  for (int i = 0; i < H; i++){
    for (int j = 0; j < W; j++){
      cin >> A[i][j];
    }
  }
  vector<vector<vector<int>>> P(H, vector<vector<int>>(W, vector<int>(4)));
  for (int i = 0; i < H; i++){
    for (int j = 0; j < W; j++){
      for (int k = 0; k < 4; k++){
        P[i][j][k] = i * dx[k] + j * dy[k];
      }
      P[i][j][3] += W - 1;
    }
  }
  vector<int> C = {H, W, H + W - 1, H + W - 1};
  vector<vector<int>> sum(4);
  for (int i = 0; i < 4; i++){
    sum[i].resize(C[i], 0);
  }
  for (int i = 0; i < H; i++){
    for (int j = 0; j < W; j++){
      for (int k = 0; k < 4; k++){
        sum[k][P[i][j][k]] += A[i][j];
      }
    }
  }
  int ans = 0;
  for (int i = 0; i < 4; i++){
    for (int j = 0; j < 4; j++){
      vector<vector<int>> sum2(C[i], vector<int>(C[j], 0));
      for (int k = 0; k < H; k++){
        for (int l = 0; l < W; l++){
          sum2[P[k][l][i]][P[k][l][j]] += A[k][l];
        }
      }
      for (int k = 0; k < C[i]; k++){
        for (int l = 0; l < C[j]; l++){
          ans = max(ans, sum[i][k] + sum[j][l] - sum2[k][l]);
        }
      }
    }
  }
  cout << ans << endl;
}