#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
//using mint = modint998244353;
//const int mod = 998244353;
//using mint = modint1000000007;
//const int mod = 1000000007;
const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int h, w; cin >> h >> w;
	vector a(h, vector<int>(w));
	vector b(h, vector<vector<int>>(w));
	rep(i, h)rep(j, w)cin >> a[i][j];
	// i,j,i+j,j-i+(h-1)
	vector<int>v0(h), v1(w), v2(h + w - 1), v3(h + w - 1);
	rep(i, h)rep(j, w) {
		v0[i] += a[i][j];
		v1[j] += a[i][j];
		v2[i + j] += a[i][j];
		v3[j - i + (h - 1)] += a[i][j];
	}
	int ans = 0;
	auto v2l = v2, v2r = v2, v3l = v3, v3r = v3;
	rep2(i, 1, h + w - 1) v2l[i] = max(v2l[i - 1], v2l[i]);
	rep2(i, 1, h + w - 1) v3l[i] = max(v3l[i - 1], v3l[i]);
	rrep(i, h + w - 2) v2r[i] = max(v2r[i + 1], v2r[i]);
	rrep(i, h + w - 2) v3r[i] = max(v3r[i + 1], v3r[i]);
	rep(i, h) {// (i,0) (i,w-1)
		//cout << i << endl;
		int val = -INF;
		if (0 != i)chmax(val, v2l[i - 1]);
		if ((h + w - 1) != i + w)chmax(val, v2r[i + w]);
		if (0 != (h - 1 - i))chmax(val, v3l[h - 2 - i]);
		if ((h + w - 1) != (w + (h - 1) - i))chmax(val, v3r[w + (h - 1) - i]);
		chmax(ans, v0[i] + val);
	}
	rep(j, w) {//(0,j),(h-1,j)
		//cout << j << endl;
		int val = -INF;
		if (0 != j)chmax(val, v2l[j - 1]);
		if ((h + w - 1) != (j + h))chmax(val, v2r[j + h]);
		if (0 != j)chmax(val, v3l[j - 1]);
		if ((h + w - 1) != (j + h))chmax(val, v3r[j + h]);
		chmax(ans, v0[j] + val);
	}
	rep(i, h)rep(j, w) {
		vector<int>v = { v0[i],v1[j],v2[i + j],v3[j - i + (h - 1)] };
		sort(allR(v));
		chmax(ans, v[0] + v[1] - a[i][j]);
	}
	rep(i, v2.size())rep(j, v3.size()) {
		int x = i;
		int y = j - (h - 1);
		if (0 == abs(x - y) % 2)continue;
		chmax(ans, v2[i] + v3[j]);
	}
	sort(allR(v0));
	if (v0.size() >= 2)chmax(ans, v0[0] + v0[1]);
	sort(allR(v1));
	if (v1.size() >= 2)chmax(ans, v1[0] + v1[1]);
	sort(allR(v2));
	if (v2.size() >= 2)chmax(ans, v2[0] + v2[1]);
	sort(allR(v3));
	if (v3.size() >= 2)chmax(ans, v3[0] + v3[1]);
	cout << ans << endl;
	return 0;
}