#include <bits/stdc++.h>
using namespace std;
#define maxn 55
const int inf = 0x3f3f3f3f;
int M, N;
int mp[maxn][maxn];
int mark[maxn][maxn];
int dir[4][2] = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
struct Edge
{
    int from, to, cap, flow;
    Edge(int f, int t, int c, int fl)
    {
        from = f; to = t; cap = c; flow = fl;
    }
};
vector <Edge> edges;
vector <int> G[maxn*maxn];
int s, t, n, m;
int cur[maxn*maxn], vis[maxn*maxn], d[maxn*maxn];
void AddEdge(int from, int to, int cap)
{
    edges.push_back(Edge(from, to, cap, 0));
    edges.push_back(Edge(to, from, 0, 0));
    m = edges.size();
    G[from].push_back(m-2);
    G[to].push_back(m-1);
}
bool bfs()
{
    memset(vis, 0, sizeof(vis));
    d[s] = 0; vis[s] = 1;
    queue <int> q;
    q.push(s);
    while(!q.empty())
    {
        int u = q.front(); q.pop();
        for(int i = 0; i < G[u].size(); i++)
        {
            Edge &e = edges[G[u][i]];
            if(!vis[e.to] && e.cap > e.flow)
            {
                vis[e.to] = 1;
                d[e.to] = d[u]+1;
                q.push(e.to);
            }
        }
    }
    return vis[t];
}
int dfs(int x, int a)
{
    if(x == t || a == 0) return a;
    int flow = 0, f;
    for(int &i = cur[x]; i < G[x].size(); i++)
    {
        Edge &e = edges[G[x][i]];
        if(d[x]+1 == d[e.to] && (f = dfs(e.to, min(a, e.cap-e.flow))) > 0)
        {
            e.flow += f;
            edges[G[x][i]^1].flow -= f;
            flow += f;
            a -= f;
            if(a == 0) break;
        }
    }
    return flow;
}
int Maxflow()
{
    int flow = 0;
    while(bfs())
    {
        memset(cur, 0, sizeof(cur));
        flow += dfs(s, inf);
    }
    return flow;
}
bool judge(int x, int y)
{
    if(x >= 1 && x <= N && y >= 1 && y <= M) return true;
    return false;
}
int main()
{    
    while(~scanf("%d%d", &N, &M))
    {
        edges.clear();
        for(int i = 0; i < maxn*maxn; i++) G[i].clear();
        int sum = 0;
        for(int i = 1; i <= N; i++)
        {
            for(int j = 1; j <= M; j++)
            {
                scanf("%d", &mp[i][j]);
                sum += mp[i][j];
            }
        }
        s = 0; t = N*M+1;
        for(int i = 1; i <= N; i++)
        {
            for(int j = 1; j <= M; j++)
            {
                if((i+j)%2 == 0) 
                {
                    AddEdge(s, (i-1)*M+j, mp[i][j]);    
                    if(i > 1) AddEdge((i-1)*M+j, (i-2)*M+j, inf);
                    if(j > 1) AddEdge((i-1)*M+j, (i-1)*M+j-1, inf);
                    if(i < N) AddEdge((i-1)*M+j, i*M+j, inf);
                    if(j < M) AddEdge((i-1)*M+j, (i-1)*M+j+1, inf);
                }
                else AddEdge((i-1)*M+j, t, mp[i][j]);
            }
        }
        printf("%d\n", sum - Maxflow());
    }

}