#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 == N-1 && j == M-2) || (j == M-1 && i == N-2)) {
                if(mn == -1) mn = v;
                else mn = min(mn,v);
            }  

        }
    }

    if(M % 2 == 1 || M % 2 == 1) {
        cout << sum;
        return sum;
    
    }

    sum -= mn;
    
    cout << sum;
    return sum;







}