#include <iostream>
#include <string>
#include <vector>
#include <cmath>
#include <algorithm>
#include <numeric>

using namespace std;

int main() 
{
    int n, m;
    cin >> n >> m;
    vector<int> a(n * m);
    for (auto& x : a) cin >> x;

    if (n % 2 || m % 2)
    {
        cout << std::accumulate(a.begin(), a.end(), 0) << '\n';
        return 0;
    }

    int mn = 1000000000;
    for (int i = 0; i < n; ++i)
    {
        for (int j = 0; j < m; ++j)
        {
            if ((i + j) % 2 == 1)
            {
                mn = min(mn, a[i * m + j]);
            }
        }
    }    

    cout << (std::accumulate(a.begin(), a.end(), 0) - mn) << '\n';
    return 0;
}