1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 using namespace std;
 5
 6 int n,m,tot;
 7 int mp[205][205], head[40005], mark[40005];
 8 bool vis[40005];
 9
10 struct node
11 {
12     int v,next;
13 }e[8*40005];
14
15 int dx[] = {-2,-2,-1,-1,1,1,2,2};
16 int dy[] = {1,-1,2,-2,2,-2,1,-1};
17
18 void addEdge(int u, int v)
19 {
20     e[tot].v = v;
21     e[tot].next = head[u];
22     head[u] = tot++;
23 }
24
25 bool match(int u)
26 {
27     for(int i=head[u];i!=-1;i=e[i].next)
28     {
29         int v = e[i].v;
30         if(!vis[v])
31         {
32             vis[v] = true;
33             if(mark[v]==-1 || match(mark[v]))
34             {
35                 mark[v] = u;
36                 return true;
37             }
38         }
39     }
40     return false;
41 }
42
43 int main()
44 {
45     //freopen("in.txt","r",stdin);
46     int num = 0;
47     scanf("%d%d",&n,&m);
48     for(int i=1;i<=n;i++)
49     for(int j=1;j<=m;j++)
50     {
51         scanf("%d",&mp[i][j]);
52         if(mp[i][j]) num++;
53     }
54     tot = 0;
55     memset(head,-1,sizeof(head));
56     for(int i=1;i<=n;i++)
57     for(int j=1;j<=m;j++)
58     {
59         if(!mp[i][j])
60         {
61             for(int k=0;k<8;k++)
62             {
63                 int x = i+dx[k];
64                 int y = j+dy[k];
65                 if(x<1 || x>n || y<1 || y>m)  continue;
66                 if(mp[x][y]==1)  continue;
67                 int p1 = (i-1)*m+j;
68                 int p2 = (x-1)*m+y;
69                 addEdge(p1,p2);
70             }
71         }
72     }
73     int sum = 0;
74     memset(mark,-1,sizeof(mark));
75     for(int i=1;i<=n*m;i++)
76     {
77         memset(vis,false,sizeof(vis));
78         if(match(i))  sum++;
79     }
80     printf("%d\n",n*m-num-sum/2);
81     return 0;
82 }