#include <iostream>
#include <vector>
#include <cmath>
using namespace std;

int main(){
    int N, M;
    cin >> N >> M;

    int sum = 0;

    int mn = -1;

    for(int i = 0; i < N; i++) {
        for(int j = 0; j < M; j++) {
            int v;
            cin >> v;
            sum += v;

            if((i == 0 && j == 0) || (i ==  N-1 && j == M-1)) {
                continue;
            }

            if(mn == -1) {
                mn = v;
            } else {
                mn = min(mn,v);
            }

        }
    }

    if(M % 2 == 1 || N % 2 == 1) {
        cout << sum << "\n";
        return 0;
    }

    sum -= mn;

    cout << sum << "\n";







}