#include <iostream>
#include <queue>
#include <cstring>
using namespace std;
#define ios ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
const int N = 20010, M = 100010;
typedef long long LL;

struct edge{
    LL v, c, ne;
}e[M * 2];
int h[N], idx = 1, cur[N], d[N];
int n, m, S, T;

void add(int u, int v, int w){
    e[++ idx] = {v, w, h[u]};
    h[u] = idx;
}

bool bfs(){
    memset(d, 0, sizeof d);
    queue<int> q;
    d[S] = 1, q.push(S);
    while(q.size()){
        int u = q.front(); q.pop();
        for(int i = h[u]; i; i = e[i].ne){
            int v = e[i].v;
            if(d[v] == 0 && e[i].c){
                d[v] = d[u] + 1;
                q.push(v);
                if(v == T) return true;
            }
        }
    }
    return false;
}

LL dfs(int u, LL mf){
    if(u == T) return mf;
    LL s = 0;
    for(int i = cur[u]; i; i = e[i].ne){
        cur[u] = i;
        int v = e[i].v;
        if(d[v] == d[u] + 1 && e[i].c){
            int f = dfs(v, min(mf, e[i].c));
            e[i].c -= f, e[i ^ 1].c += f;
            s += f, mf -= f;
            if(mf == 0) break;
        }
    }
    if(s == 0) d[u] = 0;
    return s;
}


LL dinic(){
    LL res = 0;
    while(bfs()){
        memcpy(cur, h, sizeof h);
        res += dfs(S, 1e9);
    }
    return res;
}

int dir[4][2] = {
    {0, 1}, {1, 0}, {0, -1}, {-1, 0}
};

int main(){
    ios
    cin >> n >> m;
    S = 0, T = n * m + 1;
    LL s = 0;
    for(int i = 1; i <= n; i++)
        for(int j = 1; j <= m; j++){
            int x; cin >> x;
            s += x;
            int u = (i - 1) * m + j;
            if((i + j) & 1){
                add(S, u, x), add(u, S, 0);
                for(int k = 0; k <= 4; k++){
                    int x = i + dir[k][0], y = j + dir[k][1];
                    if(x >= 1 && x <= n && y >= 1 && y <= m){
                        int v = (x - 1) * m + y;
                        add(u, v, 1e9), add(v, u, 0);
                    }
                }
            }
            else add(u, T, x), add(T, u, 0);
            
        }
    cout << s - dinic();
    
    return 0;
}