#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef double ld;

int main()
{
    int n, m;
    cin >> n >> m;

    vector<vector<int>> p(n, vector<int>(m));

    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < m; j++)
        {
            cin >> p[i][j];
        }
    }

    ll ans = 0;
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < m; j++)
        {
            ans += p[i][j];
        }
    }
    if ((n % 2 == 1) or (m % 2 == 1))
    {
        cout << ans << endl;
    }
    else
    {
        ll min = 99999999;
        for (int i = 1; i < m; i++)
        {
            if (p[0][i] < min)
                min = p[0][i];
        }
        if (m > 2)
        {
            for (int i = 0; i < m; i++)
            {
                if (p[1][i] < min)
                    min = p[1][i];
            }
            for (int i = 0; i < m; i++)
            {
                if (p[n - 2][i] < min)
                    min = p[n - 2][i];
            }
        }
        for (int i = 0; i < m - 1; i++)
        {
            if (p[n - 1][i] < min)
                min = p[n - 1][i];
        }

        ///////

        for (int i = 1; i < n; i++)
        {
            if (p[i][0] < min)
                min = p[i][0];
        }
        if (n > 2)
        {
            for (int i = 0; i < n; i++)
            {
                if (p[i][1] < min)
                    min = p[i][1];
            }
            for (int i = 0; i < n; i++)
            {
                if (p[i][m - 2] < min)
                    min = p[i][m - 2];
            }
        }
        for (int i = 0; i < n - 1; i++)
        {
            if (p[i][m - 1] < min)
                min = p[i][m - 1];
        }

        cout << ans - min << endl;
    }

    return 0;
}