#include <string>
#include <vector>
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<stack>
#include<queue>
#include<cmath>
#include<algorithm>
#include<functional>
#include<list>
#include<deque>
#include<bitset>
#include<set>
#include<map>
#include<unordered_map>
#include<unordered_set>
#include<cstring>
#include<sstream>
#include<complex>
#include<iomanip>
#include<numeric>
#include<cassert>
#define X first
#define Y second
#define pb push_back
#define rep(X,Y) for (int (X) = 0;(X) < (Y);++(X))
#define reps(X,S,Y) for (int (X) = S;(X) < (Y);++(X))
#define rrep(X,Y) for (int (X) = (Y)-1;(X) >=0;--(X))
#define repe(X,Y) for ((X) = 0;(X) < (Y);++(X))
#define peat(X,Y) for (;(X) < (Y);++(X))
#define all(X) (X).begin(),(X).end()
#define rall(X) (X).rbegin(),(X).rend()
#define eb emplace_back
#define UNIQUE(X) (X).erase(unique(all(X)),(X).end())

using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
template<class T> using vv=vector<vector<T>>;
template<class T> ostream& operator<<(ostream &os, const vector<T> &t) {
os<<"{"; rep(i,t.size()) {os<<t[i]<<",";} os<<"}"<<endl; return os;}
template<class S, class T> ostream& operator<<(ostream &os, const pair<S,T> &t) { return os<<"("<<t.first<<","<<t.second<<")";}
template<class T> inline bool MX(T &l,const T &r){return l<r?l=r,1:0;}
template<class T> inline bool MN(T &l,const T &r){return l>r?l=r,1:0;}
const ll MOD=1e9+7;
const ll INF=1e13;
ll a[2222][2222];
ll dp[422][222][222];

int main(){
  ios_base::sync_with_stdio(false);
  cout<<fixed<<setprecision(0);
  int n,m;
  cin>>n>>m;
  rep(i,n)rep(j,m) cin>>a[i][j];
  fill(dp[0][0],dp[0][0]+422*222*222,-INF);
  dp[0][0][0]=0;
  rep(i,n+m-1)rep(j,m)rep(k,j+1){
    if(i-j>=0){
      dp[i][j][k]+=a[i-j][j];
      if(j!=k) dp[i][j][k]+=a[i-k][k];
    }
    rep(a,2)rep(b,2) MX(dp[i+1][j+a][k+b],dp[i][j][k]);
  }
  cout<<dp[n+m-2][m-1][m-1]<<endl;
  return 0;
}
