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

using namespace std;

int main(){

    int N, M;
    cin >> N >> M;
    int minimum = INT32_MAX;
    int sum = 0;

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

        if (i != 0 && i != (N*M) - 1){
            minimum = min(minimum, a);
        }
    }

    //cout << "sum: " << sum << ", min: " << minimum << endl; 

    if (N % 2 == 0 && M % 2 == 0){
        sum -= minimum;
    }

    cout << sum << endl;

    return 0;
}