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

const vector<int> dx = {0, 1, 1, 1};
const vector<int> dy = {1, 0, 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<tuple<int, int, int>> start;
	start.push_back(make_tuple(0, 0, 2));
	for (int i = 1; i <= w; i++) {
		start.push_back(make_tuple(0, i, 1));
		start.push_back(make_tuple(0, i, 2));
		start.push_back(make_tuple(0, i, 3));
	}
	start.push_back(make_tuple(0, w + 1, 3));
	for (int i = 1; i <= h; i++) {
		start.push_back(make_tuple(i, 0, 0));
		start.push_back(make_tuple(i, 0, 2));
		start.push_back(make_tuple(i, 0, 3));
	}
	long long ans = 0;
	for (tuple<int, int, int> T1 : start) {
		for (tuple<int, int, int> T2 : start) {
			long long res = 0;
			int x1, y1, d1, x2, y2, d2;
			tie(x1, y1, d1) = T1;
			tie(x2, y2, d2) = T2;
			x1 += dx[d1];
			y1 += dy[d1];
			x2 += dx[d2];
			y2 += dy[d2];
			set<pair<int, int>> st;
			while (1 <= x1 && x1 <= h && 1 <= y1 && y1 <= w) {
				res += A[x1 - 1][y1 - 1];
				st.insert(make_pair(x1, y1));
				x1 += dx[d1];
				y1 += dy[d1];
			}
			while (1 <= x2 && x2 <= h && 1 <= y2 && y2 <= w) {
				if (!st.count(make_pair(x2, y2))) {
					res += A[x2 - 1][y2 - 1];
				}
				x2 += dx[d2];
				y2 += dy[d2];
			}
			ans = max(ans, res);
		}
	}
	cout << ans << endl;
}