#include <bits/stdc++.h>

using namespace std;
using vi = vector<int>;



void solve(){
    int n, m;
    cin >> n >> m;
    int ans = 0, minimum = 1001;
    vector< vi > arr(n, vector<int>(m));
    for( int i = 0; i < n; ++i ){
        for( int j = 0; j < m; ++j){
            cin >> arr[i][j];
            ans += arr[i][j];
            if ( (i == 0 && j == 0) || (i == n - 1 && j == m - 1) ) continue;
            if (arr[i][j] < minimum )
                minimum = arr[i][j];
        }
    }
    if ( n % 2 == 1 || m % 2 == 1){
        cout << ans << endl;
        return;
    }
    cout << ans - minimum << endl;
    return;
}

int main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);
    int t = 1;
    //cin >> t;
    while (t--){
        solve();
    }
    return 0;
}