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

int main() {
	int H, W;
	cin >> H >> W;
	vector<int> x = {1, 0, 1, 1};
	vector<int> y = {0, 1, 1, -1};
	vector<map<int, long long>> s(4);
	vector<vector<long long>> A(H, vector<long long>(W));
	for( int i = 0; i < H; i++ ) {
		for( int j = 0; j < W; j++ ) {
			cin >> A[i][j];
			for( int k = 0; k < 4; k++ ) {
				s[k][x[k]*i+y[k]*j] += A[i][j];
			}
		}
	}
	long long ans = 0;
	for( int i = -1000; i <= 1000; i++ ) {
		for( int j = -1000; j <= 1000; j++ ) {
			for( int k = 0; k < 4; k++ ) {
				for( int l = 0; l < 4; l++ ) {
				  if( k == l ) continue;
					if( 0 <= i && i < H && 0 <= j && j < W ) ans = max(ans, s[k][x[k]*i+y[k]*j]+s[l][x[l]*i+y[l]*j]-A[i][j]);
					else  ans = max(ans, s[k][x[k]*i+y[k]*j]+s[l][x[l]*i+y[l]*j]);
				}
			}
		}
	}
	for( int i = 0; i < 4; i++ ) {
		vector<long long> v = {0};
		for( auto [j, k] : s[i] ) v.push_back(k);
		sort(v.rbegin(), v.rend());
		ans = max(ans, v[0]+v[1]);
	}
	cout << ans << endl;
}