#include<iostream>

 #include<cstdio>

 #include<cstring>

 using namespace std;

 int n,m,tot;

 int mp[][], head[], mark[];

 bool vis[];

 struct node

 {

     int v,next;

 }e[*];

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

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

 void addEdge(int u, int v)

 {

     e[tot].v = v;

     e[tot].next = head[u];

     head[u] = tot++;

 }

 bool match(int u)

 {

     for(int i=head[u];i!=-;i=e[i].next)

     {

         int v = e[i].v;

         if(!vis[v])

         {

             vis[v] = true;

             if(mark[v]==- || match(mark[v]))

             {

                 mark[v] = u;

                 return true;

             }

         }

     }

     return false;

 }

 int main()

 {

     //freopen("in.txt","r",stdin);

     int num = ;

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

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

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

     {

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

         if(mp[i][j]) num++;

     }

     tot = ;

     memset(head,-,sizeof(head));

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

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

     {

         if(!mp[i][j])

         {

             for(int k=;k<;k++)

             {

                 int x = i+dx[k];

                 int y = j+dy[k];

                 if(x< || x>n || y< || y>m)  continue;

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

                 int p1 = (i-)*m+j;

                 int p2 = (x-)*m+y;

                 addEdge(p1,p2);

             }

         }

     }

     int sum = ;

     memset(mark,-,sizeof(mark));

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

     {

         memset(vis,false,sizeof(vis));

         if(match(i))  sum++;

     }

     printf("%d\n",n*m-num-sum/);

     return ;

 }