C++ :

#include<bits/stdc++.h>
using namespace std;

#define gc (c=getchar())
int read()
{
	char c;
	while(gc<'0');
	int x=c-'0';
	while(gc>='0')x=x*10+c-'0';
	return x;
}
#define rep(i,l,r) for(int i=l;i<=r;++i)
namespace flow
{
const int N=1050,M=4*1000*2+5,oo=2139062143;
int n,S,T;
int t[N],a[N],g[N];
struct edge
{
	int to,next,f;
}l[M];int e=1;
void add_e(int x,int y,int f=oo)
{
	l[++e]=(edge){y,t[x],f};t[x]=e;
	l[++e]=(edge){x,t[y],0};t[y]=e;
}
int dfs(int x,int f)
{
	if(x==T)return f;
	int f0=f;
	for(int &i=a[x],y;y=l[i].to;i=l[i].next)
	if(l[i].f&&g[y]<g[x])
	{
		int del=dfs(y,min(f,l[i].f));
		l[i].f-=del;l[i^1].f+=del;
		f-=del;
		if(!f) return f0;
	}
	return f0-f;
}
int q[N],head,tail;
bool bfs()
{
	memset(g+1,(1<<7)-1,n*sizeof(int));
	g[T]=0;
	tail=1;q[1]=T;
	for(int head=1;head<=tail;++head)
	{
		int x=q[head];
		for(int i=t[x],y;y=l[i].to;i=l[i].next)
		if(l[i^1].f&&g[y]==2139062143) 
		{
			g[y]=g[x]+1;
			if(y==S)return 1;
			q[++tail]=y;
		}
	}
	return 0;
}
int max_flow()
{
	int ans=0;
	while(bfs()) 
	{
	  memcpy(a+1,t+1,n*sizeof(int));
	  ans+=dfs(S,oo);
	}
	return ans;
}
void write(int x)
{
	for(int i=t[x],y;y=l[i].to;i=l[i].next)
	if(l[i].f&&y!=T) printf("%d ",y);
	puts("");
}
};

int main()
{
	//freopen("1.in","r",stdin);
	int n,m;
	scanf("%d%d",&n,&m);
	
	flow::n=n*m+2;flow::S=flow::n-1;flow::T=flow::n;
	int now=0,sum=0;
	rep(i,1,n) 
	rep(j,1,m)
	{
		++now;
		int w=read();sum+=w;
	  if(i+j&1) flow::add_e(now,flow::T,w);
	  else
	  {flow::add_e(flow::S,now,w);
	   if(i!=1) flow::add_e(now,now-m);
	   if(i!=n) flow::add_e(now,now+m);
	   if(j!=1) flow::add_e(now,now-1);
	   if(j!=m) flow::add_e(now,now+1);
	  }
    }
    cout<<sum-flow::max_flow();
}