/*最大点权独立集=sum-最小点权覆盖*/
#include<stdio.h>
#include<string.h>
#include<queue>
using namespace std;
#define inf 0x3fffffff
#define ll __int64
#define N 3000
struct node
{
ll u,v,w,next;
}bian[N*N*2];
ll ma[N][N],id[N][N],head[N],yong,s,t,dis[N];;
void addedge(ll u,ll v,ll w)
{
bian[yong].u=u;
bian[yong].v=v;
bian[yong].w=w;
bian[yong].next=head[u];
head[u]=yong++;
}
void add(ll u,ll v,ll w)
{
addedge(u,v,w);
addedge(v,u,0);
}
void init()
{
yong=0;
memset(head,-1,sizeof(head));
memset(dis,-1,sizeof(dis));
}
void bfs()
{
ll u,v,i;
queue<ll>q;
q.push(t);
dis[t]=0;
while(!q.empty())
{
u=q.front();
q.pop();
for(i=head[u]; i!=-1; i=bian[i].next)
{
v=bian[i].v;
if(dis[v]==-1)
{
dis[v]=dis[u]+1;
q.push(v);
}
}
}
return ;
}
ll ISAP()
{
ll sum=0;
bfs();
ll gap[N],cur[N],stac[N],top,i;
memset(gap,0,sizeof(gap));
for(i=s; i<=t; i++)
{
gap[dis[i]]++;
cur[i]=head[i];
}
ll k=s;
top=0;
while(dis[s]<t+1)
{
if(k==t)
{
ll minn=inf,index;
for(i=0; i<top; i++)
{
ll e=stac[i];
if(minn>bian[e].w)
{
minn=bian[e].w;
index=i;
}
}
for(i=0; i<top; i++)
{
ll e=stac[i];
bian[e].w-=minn;
bian[e^1].w+=minn;
}
sum+=minn;
top=index;
k=bian[stac[top]].u;
}
for(i=cur[k]; i!=-1; i=bian[i].next)
{
ll v=bian[i].v;
if(bian[i].w&&dis[k]==dis[v]+1)
{
cur[k]=i;
k=v;
stac[top++]=i;
break;
}
}
if(i==-1)
{
ll m=t+1;
for(i=head[k]; i!=-1; i=bian[i].next)
if(m>dis[bian[i].v]&&bian[i].w)
{
m=dis[bian[i].v];
cur[k]=i;
}
if(--gap[dis[k]]==0)break;
gap[dis[k]=m+1]++;
if(k!=s)
k=bian[stac[--top]].u;
}
}
return sum;
}
int main()
{
ll n,m,i,j,cnt;
ll sum;
while(scanf("%I64d%I64d",&n,&m)!=EOF)
{
init();
cnt=1;
sum=0;s=0;t=n*m+1;
for(i=1; i<=n; i++)
for(j=1; j<=m; j++)
{
scanf("%I64d",&ma[i][j]);
id[i][j]=cnt++;
sum+=ma[i][j];
}
for(i=1; i<=n; i++)
for(j=1; j<=m; j++)
{
if((i+j)&1)
{
add(s,id[i][j],ma[i][j]);
if(i<=n-1)
add(id[i][j],id[i+1][j],inf);
if(j<=m-1)
add(id[i][j],id[i][j+1],inf);
if(i>=2)
add(id[i][j],id[i-1][j],inf);
if(j>=2)
add(id[i][j],id[i][j-1],inf);
}
else
add(id[i][j],t,ma[i][j]);
}
printf("%I64d
",sum-ISAP());
}
return 0;
}