#include <iostream>
#include <vector>

using namespace std;

int main()
{
    int rows;
    int cols;
    cin >> rows >> cols;
    vector<vector<int>> elements(rows, vector<int>(cols, 0));

    if (rows % 2 == 0 && cols % 2 == 0)
    {
        int summary = 0;
        int min = __INT32_MAX__;
        for (int y = 0; y < rows; y++)
        {
            for (int x = 0; x < cols; x++)
            {
                int in;
                cin >> in;
                summary += in;

                if (y % 2 == 0 && x % 2 != 0)
                {
                    if (min >= in)
                    {
                        min = in;
                    }
                }
                if (y % 2 != 0 && x % 2 == 0)
                {
                    if (min >= in)
                    {
                        min = in;
                    }
                }
            }
        }
        summary -= min;
        cout << summary;
    }
    else
    {
        int summary = 0;
        for (int y = 0; y < rows; y++)
        {
            for (int x = 0; x < cols; x++)
            {
                int in;
                cin >> in;
                summary += in;
            }
        }
        cout << summary;
    }
}