#include <cstdio>
#include <cstring>
#include <vector>
#include <queue>
using namespace std;
const int INF=0x3f3f3f3f;
const int MAX_V=20010;
struct edge{int to,cap,rev;};
vector<edge> G[MAX_V];
int level[MAX_V],iter[MAX_V];
void add_edge(int from,int to,int cap){G[from].push_back((edge){to,cap,G[to].size()});G[to].push_back((edge){from,0,G[from].size()-1});
}
void bfs(int s){memset(level,-1,sizeof(level));queue<int> que;level[s]=0;que.push(s);while(!que.empty()){int v=que.front(); que.pop();for(int i=0;i<G[v].size();i++){edge &e=G[v][i];if(e.cap>0&&level[e.to]<0){level[e.to]=level[v]+1;que.push(e.to);}}}
}
int dfs(int v,int t,int f){if(v==t)return f;for(int &i=iter[v];i<G[v].size();i++){edge &e=G[v][i];if(e.cap>0&&level[v]<level[e.to]){int d=dfs(e.to,t,min(f,e.cap));if(d>0){e.cap-=d;G[e.to][e.rev].cap+=d;return d;}}}return 0;
}
int max_flow(int s,int t){int flow=0;for(;;){bfs(s);if(level[t]<0)return flow;memset(iter,0,sizeof(iter));int f;while((f=dfs(s,t,INF))>0){flow+=f;}}
}
int n,m;
int mp[110][110];
const int dx[]={1,-1,0,0},dy[]={0,0,1,-1};
bool check(int x,int y){return x<n&&x>=0&&y<m&&y>=0;}
int main(){while(~scanf("%d%d",&n,&m)){int s=n*m,t=s+1;for(int i=0;i<=t;i++)G[i].clear();for(int i=0;i<n;i++)for(int j=0;j<m;j++){scanf("%d",&mp[i][j]);for(int k=0;k<4;k++){int x=i+dx[k],y=j+dy[k];if(check(x,y))add_edge(i*m+j,x*m+y,1);}if(mp[i][j]==1)add_edge(s,i*m+j,INF);if(mp[i][j]==2)add_edge(i*m+j,t,INF);}printf("%d\n",max_flow(s,t));}return 0;
}