#include <bits/stdc++.h>

using namespace std;

#define rep(i, a, b) for(int i=a; i<b; i++)
#define all(x) begin(x), end(x)
#define sz(x) (int) (x).size()
#define fo(i, n) rep(i, 0, n)
#define F first
#define S second
#define MP make_pair
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vll;

int main() {
	cin.tie(0)->sync_with_stdio(0);
	cin.exceptions(cin.failbit);
	int n, m;
	cin >> n >> m;
	ll s = 0;
	int x, mn = (m%2 || n%2) ? 0 : 100000;
	for (int i=0; i<n; i++) {
		for (int j=0; j<m; j++) {
				cin >> x;
				s += x;
				if ((i % 2) == (j % 2)) {} else {
						mn = min(x, mn);
				}
		}
	}
	cout << s - mn << endl;
}