#include <bits/stdc++.h>
using namespace std;

struct p{ double x,y; };

p psub(p a,p b){ return {a.x-b.x,a.y-b.y};}

double dst(p a, p b, p c, p d){
    a = psub(a,b); c = psub(c,d);
    double ret = a.x*c.y - a.y*c.x;
    return ret;
}

pair<int,int> crossP(p a, p b, p c, p d){
    double D = dst(b,a,d,c), s = dst(c,a,d,c), t = dst(b,a,a,c);
    s /= D; t /= D;
    if(D == 0.0) return {-1e9,-1e9};
    if(s < 0.0 || 1.0 < s || t < 0.0 || 1.0 < t){return {-1e9,-1e9};}

    return {a.x + s*(b.x-a.x), a.y + s*(b.y-a.y)};  
}

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int H,W; cin >> H >> W;
    vector<vector<int>> A(H,vector<int>(W));
    for(auto &h : A) for(auto &w : h) cin >> w; 
    if(H == 1 && W == 1){cout << A.at(0).at(0) << endl; return 0;}

    vector<tuple<int,int,int,int,int,int,int>> beam;
    for(int i=0; i<H; i++){
        for(int k=0; k<W; k++){
            if(!(i == 0 || i == H-1 || k == 0 || k == W-1)) continue;

            bool one = true;
            for(int a=-1; a<=1; a++) for(int b=0; b<=1; b++){
                if(a == 0 && b == 0) continue;
                if(i == 0 && a == -1) continue;
                if(i == H-1 && a == 1) continue;
                if(k == W-1 && i != 0) continue;
                if(a == 0 && b == 1 && k != 0) continue;
                if(a == 1 && b == 0 && i != 0) continue;

                int x = i, y = k, p = 0,grid = 0, i2 = 0,k2 = 0;
                while(true){
                    p += A.at(x).at(y); grid++;

                    x += a; y += b;
                    if(x < 0 || x >= H || y < 0 || y >= W){
                        i2 = x-a; k2  = y-b;
                        break;
                    }
                }
                if(!one && grid == 1) continue;
                if(one && grid == 1) one = false;
                
                beam.push_back({i,k,i2,k2,a,b,p});
            }
        }
    }

    int bs = beam.size(),answer = 0;
    for(int i=0; i<bs; i++){
        auto [x1,y1,x2,y2,a1,b1,p1] = beam.at(i);
        for(int k=i+1; k<bs; k++){
            auto [x3,y3,x4,y4,a2,b2,p2] = beam.at(k);
            
            int now = p1+p2; bool check = true;
            if(a1 == a2 && b1 == b2) check = false;
            if(a1 == 1 && b1 == -1 && a2 == -1 && b2 == 1 && (x1+y1)%2 == (x3+y3)%2) check = false;
            if(a1 == -1 && b1 == 1 && a2 == 1 && b2 == -1 && (x1+y1)%2 == (x3+y3)%2) check = false;

            if(check){
                auto[cx,cy] = crossP(p{x1+0.0,y1+0.0},p{x2+0.0,y2+0.0},p{x3+0.0,y3+0.0},p{x4+0.0,y4+0.0});
                if(cx >= 0 && cx < H && cy >= 0 && cy < W) now -= A.at(cx).at(cy);
            }
            answer = max(answer,now);
        }
    }
    cout << answer << endl;
}