#include<cmath>

 #include<queue>

 #include<vector>

 #include<cstdio>

 #include<cstring>

 #include<iostream>

 #include<algorithm>

 #define FOR(a,b,c) for(int a=(b);a<=(c);a++)

 using namespace std;

 const int N = 1e4+;

 const int inf = 1e9;

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

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

 struct Edge{ int u,v,cap,flow;

 };

 struct Dinic {

     int n,m,s,t;

     int d[N],cur[N],vis[N];

     vector<Edge> es;

     vector<int> g[N];

     queue<int> q;

     void init(int n) {

         this->n=n;

         es.clear();

         for(int i=;i<=n;i++) g[i].clear();

     }

     void AddEdge(int u,int v,int w) {

         es.push_back((Edge){u,v,w,});

         es.push_back((Edge){v,u,,});

         m=es.size();

         g[u].push_back(m-),

         g[v].push_back(m-);

     }

     bool bfs() {

         memset(vis,,sizeof(vis));

         q.push(s); d[s]=; vis[s]=;

         while(!q.empty()) {

             int u=q.front(); q.pop();

             for(int i=;i<g[u].size();i++) {

                 Edge& e=es[g[u][i]];

                 int v=e.v;

                 if(!vis[v] && e.cap>e.flow) {

                     d[v]=d[u]+;

                     vis[v]=;

                     q.push(v);

                 }

             }

         }

         return vis[t];

     }

     int dfs(int u,int a) {

         if(u==t || a==) return a;

         int flow=,f;

         for(int& i=cur[u];i<g[u].size();i++) {

             Edge& e=es[g[u][i]];

             int v=e.v;

             if(d[v]==d[u]+ && (f=dfs(v,min(a,e.cap-e.flow)))>) {

                 e.flow+=f;

                 es[g[u][i]^].flow-=f;

                 flow+=f; a-=f;

                 if(!a) break;

             }

         }

         return flow;

     }

     int MaxFlow(int s,int t) {

         this->s=s,this->t=t;

         int flow=;

         while(bfs()) {

             memset(cur,,sizeof(cur));

             flow+=dfs(s,inf);

         }

         return flow;

     }

 } dc;

 int n,m;

 int mp[][];

 bool inside(int x,int y)

 {

     return x>=&&x<=n&&y>=&&y<=m;

 }

 int main()

 {

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

     dc.init(n*m+);

     int s=,t=n*m+;

     FOR(i,,n) FOR(j,,m) scanf("%d",&mp[i][j]);

     FOR(i,,n) FOR(j,,m) {

         if(mp[i][j]==) dc.AddEdge(s,(i-)*m+j,inf);

         else if(mp[i][j]==) dc.AddEdge((i-)*m+j,t,inf);

         int x=i,y=j;

         if(mp[x][y]==) continue;

         FOR(k,,) {

             int nowx=x+dx[k],nowy=y+dy[k];

             if(!inside(nowx,nowy)) continue;

             if(mp[x][y]!=||mp[nowx][nowy]!=)

                 dc.AddEdge((x-)*m+y,(nowx-)*m+nowy,);

         }

     }

     printf("%d\n",dc.MaxFlow(s,t));

     return ;

 }