#include<iostream>

#include<cstdio>

#include<cstring>

#include<queue>

using namespace std;

#define N 100005

#define inf 100000005

const int d1[]={,,-,};

const int d2[]={,,,-};

int n,m,w,d[N],cur[N],S,T; bool vis[N];

queue <int> h;

int cnt=,hd[N],nxt[N],ed[N],poi[N],val[N];

inline void adde(int x,int y,int v){

    nxt[ed[x]]=++cnt, hd[x]=hd[x]?hd[x]:cnt,

    ed[x]=cnt, poi[cnt]=y, val[cnt]=v;

}

inline void link(int x,int y,int v){adde(x,y,v),adde(y,x,);}

inline int id(int x,int y){return (x-)*m+y;}

bool bfs(){

    memset(vis,,sizeof(vis));

    h.push(S); vis[S]=;

    while(!h.empty()){

        int x=h.front(); h.pop();

        for(int i=hd[x];i;i=nxt[i]){

            int to=poi[i];

            if(!vis[to]&&val[i])

                vis[to]=,d[to]=d[x]+,h.push(to);

        }

    }return vis[T];

}

int dfs(int x,int a){

    if(x==T||a==) return a;

    int F=,f;

    for(int i=cur[x];i;i=nxt[i]){

        cur[x]=i;int to=poi[i];

        if(d[to]==d[x]+&&(f=dfs(to,min(a,val[i])))>)

            a-=f,F+=f,val[i]-=f,val[i^]+=f;

    }return F;

}

int dinic(){

    int re=;

    while(bfs()){

        for(int i=;i<=T;++i) cur[i]=hd[i];

        re+=dfs(S,inf);

    }return re;

}

void draw(int x,int y){

    scanf("%d",&w); int p=id(x,y);

    for(int i=;i<;++i){

        int r1=x+d1[i],r2=y+d2[i];

        if(r1<||r1>n||r2<||r2>m) continue;

        link(p,id(r1,r2),);

    }

    if(w==) link(S,p,inf);

    if(w==) link(p,T,inf);

}

int main(){

    scanf("%d%d",&n,&m);

    S=n*m+; T=S+;

    for(int i=;i<=n;++i)

        for(int j=;j<=m;++j)

            draw(i,j);

    printf("%d",dinic());

    return ;

}