#include <bits/stdc++.h>

using namespace std;

#define ll long long 
#define rep(i,n) for(int i = 0; i<n;i++)

int main() {
    int n, m;cin>>n>>m;
    ll total = 0;

    int minm = INT32_MAX;
    rep(i,n){
        rep(j,m){
            int val;cin>>val;
            if((i%2!=1||j%2!=1)&&(i!=0||j!=0)&&(i!=n-1||j!=m-1)){
                minm = min(minm, val); 
                
            }
            total+=val;
        }
    }
    if((n&1)||(m&1))
        minm = 0;
    cout<<total-minm<<'\n';
}