#include<iostream>
using namespace std;

int main(){
    int n, m, res = 0;
    cin >> n >> m;
    if (n % 2 == 0 && m % 2 == 0){
        int x, minn = 1001;
        for (int i = 0; i < n; i++){
            for (int j = 0; j < m; j++){
                cin >> x;
                if (x < minn && (i + j) % 2 == 1)
                    minn = x;
                res += x;
            }
        }
        res -= minn;
        cout << res << endl;
        return 0;
    }
    else{
        int x;
        for (int i = 0; i < n; i++){
            for (int j = 0; j < m; j++){
                cin >> x;
                res += x;
            }
        }
        cout << res << endl;
        return 0;
    }
}