/* 
 * Problem: NOIP2008 message
 * Author: Guo Jiabao
 * Time: 2009.6.24 11:52
 * State: Solved
 * Memo: 最小费用最大流
*/
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
using namespace std;
const int MAXL=51,MAXN=MAXL*MAXL*2,MAXM=MAXN*3,INF=~0U>>1;
struct Queue
{
	int Q[MAXN],head,tail,size;
	bool inq[MAXN];
	Queue()
	{
		memset(inq,0,sizeof(inq));
		head=size =0;
		tail=-1;
	}
	void ins(int p)
	{
		inq[p]=true;
		if (++tail >= MAXN) tail = 0;
		Q[tail] = p;
		size ++;
	}
	int pop()
	{
		int p=Q[head];
		if (++head >= MAXN) head = 0;
		inq[p]=false;
		size --;
		return p;
	}
}Q;
struct edge
{
	edge *next,*op;
	int t,c,v;
}ES[MAXM],*V[MAXN],*fe[MAXN];
int N,M,EC,S,T,CostFlow;
int dist[MAXN],ft[MAXN];
inline void addedge(int a,int b,int v)
{
	ES[++EC].next = V[a]; V[a]=ES+EC; V[a]->t = b; V[a]->c=1; V[a]->v = v;
	ES[++EC].next = V[b]; V[b]=ES+EC; V[b]->t = a; V[b]->c=0; V[b]->v = -v;
	V[a]->op = V[b]; V[b]->op = V[a];
}
void init()
{
	int i,j,a,b,c;
	freopen("message.in","r",stdin);
	freopen("message.out","w",stdout);
	scanf("%d%d",&N,&M);
	for (i=1;i<=N;i++)
	{
		for (j=1;j<=M;j++)
		{
			a=(i-1)*M+j;b=a+a;a=b-1;
			scanf("%d",&c);
			addedge(a,b,c);
		}
	}
	ES[EC-1].c=ES[1].c=2;
	for (i=1;i<=N;i++)
	{
		for (j=1;j<=M;j++)
		{
			a=((i-1)*M+j)*2;
			if (j+1<=M)
			{
				b = ((i-1)*M+j+1)*2 - 1;
				addedge(a,b,0);
			}
			if (i+1<=N)
			{
				b = (i*M+j)*2 - 1;
				addedge(a,b,0);
			}
		}
	}	
	S=1; T = N * M * 2;
}
bool spfa()
{
	int i,j;
	for (i=S;i<=T;i++)
		dist[i]=-INF;
	dist[S]=0;
	Q.ins(S);
	while (Q.size)
	{
		i= Q.pop();
		for (edge *e=V[i];e;e=e->next)
		{
			j=e->t;
			if (e->c && dist[i] + e->v > dist[j])
			{
				dist[j] = dist[i] + e->v;
				ft[j] = i;
				fe[j] = e;
				if (!Q.inq[j])
					Q.ins(j);
			}
		}
	}
	return dist[T]!=-INF;
}
void aug()
{
	int i,delta=INF;
	for (i=T;i!=S;i=ft[i])
		if (fe[i]->c < delta)
			delta = fe[i]->c;
	for (i=T;i!=S;i=ft[i])
	{
		fe[i]->c -= delta;
		fe[i]->op->c +=delta;
		CostFlow += fe[i]->v * delta;
	}
}
void solve()
{
	while (spfa())
		aug();
}
int main()
{
	init();
	solve();
	printf("%d\n",CostFlow);
	return 0;
}