#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define MOD1 1000000007
#define MOD2 998244353
#define NO cout << "NO" << endl
#define YES cout << "YES" << endl
ll expo(ll a, ll b, ll mod) {ll res = 1; while (b > 0) {if (b & 1)res = (res * a) % mod; a = (a * a) % mod; b = b >> 1;} return res;}
ll mminvprime(ll a, ll b) {return expo(a, b - 2, b);}
ll mod_add(ll a, ll b, ll m) {a = a % m; b = b % m; return (((a + b) % m) + m) % m;}
ll mod_mul(ll a, ll b, ll m) {a = a % m; b = b % m; return (((a * b) % m) + m) % m;}
ll mod_sub(ll a, ll b, ll m) {a = a % m; b = b % m; return (((a - b) % m) + m) % m;}
ll mod_div(ll a, ll b, ll m) {a = a % m; b = b % m; return (mod_mul(a, mminvprime(b, m), m) + m) % m;}
void print(vector<int> &ans){for(auto x: ans) cout<<x<<" "; cout<<endl;}

// ========================================================================================================================================================================================================
vector<int> nrow={1,0};
vector<int> ncol={0,1};

void recursion(vector<vector<int>> &matrix,ll n ,ll m,ll i,ll j,ll &sum,ll &ans,vector<vector<int>> &visited)
{

  if(i==n-1 && j==m-1)
  {

    if(sum>ans)
        ans=sum;
    return;
  }

  for(int k=0;k<2;k++)
  {
    ll delrow=i+nrow[k];
    ll delcol=j+ncol[k];

    if(delrow<n && delrow>=0 && delcol>=0 && delcol<m)
    {

        if(visited[delrow][delcol]==0)
        {
            visited[delrow][delcol]=1;
            sum+=matrix[delrow][delcol];

            recursion(matrix,n,m,delrow,delcol,sum,ans,visited);

            visited[delrow][delcol]=0;
            sum-=matrix[delrow][delcol];
        }

    }

  }
}

void solve()
{
  ll n,m;cin>>n>>m;
  ll ans=0;
  vector<vector<int>> matrix(n,vector<int>(m,0));
  vector<vector<int>> visited(n,vector<int>(m,0));
  for(int i=0;i<n;i++)
  {
    for(int j=0;j<m;j++)
    {
        int e;cin>>e;
        matrix[i][j]=e;
    }
  }
  ll sum=0;
  recursion(matrix,n,m,0,-1,sum,ans,visited);
  cout<<ans<<endl;



}


int main()
{
    solve();
}