#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using ll = long long;
#define rep(i,n) for(int i=0;i<(int)(n);i++)
using mint = atcoder::modint1000000007;

int main(){
	int h,w;
	cin>>h>>w;
	vector<vector<ll>> a(h,vector<ll>(w));
	rep(i,h) rep(j,w) cin>>a[i][j];
	vector<int> dx={-1,0,1,1};
	vector<int> dy={1,1,1,0};
	auto isok=[&](int x,int y){
		return 0<=x&&x<h&&0<=y&&y<w;
	};
	auto select=[&](int x1,int y1,int i,int x2,int y2,int j){
		set<int> stl;
		ll res=0;
		while(isok(x1,y1)){
			res+=a[x1][y1];
			stl.insert(x1+y1*h);
			x1+=dx[i];
			y1+=dy[i];
		}
		while(isok(x2,y2)){
			if(!stl.count(x2+y2*h)){
				res+=a[x2][y2];
			}
			x2+=dx[j];
			y2+=dy[j];
		}
		return res;
	};
	ll ans=0;
	rep(ch1,h+w-1){
		int x1=0,y1=0;
		if(ch1>=h) y1=ch1-h+1;
		else x1=ch1;
		rep(lp,2){
			for(int ch2=ch1;ch2<h+w-1;ch2++){
				int x2=0,y2=0;
				if(ch2>=h) y2=ch2-h+1;
				else x2=ch2;
				rep(rp,2){
					rep(i,4){
						rep(j,4){
							ans=max(ans,select(x1,y1,i,x2,y2,j));
						}
					}
					if(x2!=0) break;
					x2=h-1;
				}
			}
			if(x1!=0) break;
			x1=h-1;
		}
	}
	cout<<ans<<endl;
}