#include <bits/stdc++.h>
#include <iostream>
#include <vector>

#define DEBUG true

#define $(x) {if (DEBUG) {std::cout << "(line " << __LINE__ << ") "; {x} std::cout << std::endl;}}
#define _(x) {std::cout << #x << " = " << x << " ";}

int main()
{
    int N, M;
    std::cin >> N >> M;
//    $(_(N));
//    $(_(M));
    std::vector<std::vector<int>> arr(N, std::vector<int>(M, 0));
    long sum = 0;
    long min = 1000;
    int tmp;
    for (int n = 0; n < N; n++) {
        for (int m = 0; m < M; m++) {
            std::cin >> tmp;
            sum += tmp;
            if ((n + m) % 2 == 1 && tmp < min) {
                min = tmp;
            }
        }
    }
    if (N % 2 == 0 && M % 2 == 0) {
        std::cout << (sum - min) << "\n";
    } else {
        std::cout << sum << "\n";
    }
    return 0;
}