#include<bits/stdc++.h>
#define ll long long 
using namespace std;
int n,m,S,T;
const int M=1e6,N=1e4,I=1e9;
int cn=1,to[M],flow[M],nxt[M],hd[N];
void add(int u,int v,int w){
    to[++cn]=v,nxt[cn]=hd[u],flow[cn]=w,hd[u]=cn;
    to[++cn]=u,nxt[cn]=hd[v],flow[cn]=0,hd[v]=cn;
}
int d[N];queue<int>q;
bool bfs(){
	memset(d,0,sizeof(d));
	q.push(S);d[S]=1;
	while(!q.empty()){
		int u=q.front();q.pop();
		for(int i=hd[u];i;i=nxt[i])if(flow[i]&&!d[to[i]]){
			d[to[i]]=d[u]+1;
			q.push(to[i]);
		}
	}
	return d[T]>0;
}
int dfs(int u,int in){
    if(u==T)return in;
    int out=0;
    for(int i=hd[u];i&&in;i=nxt[i])if(flow[i]&&d[to[i]]==d[u]+1){
        int p=dfs(to[i],min(in,flow[i]));
        in-=p,out+=p,flow[i]-=p,flow[i^1]+=p;
    }
    if(!out)d[u]=0;return out;
}
int id[60][60];
char cc[60];
int main(){
    scanf("%d%d",&n,&m);S=n*m*2+1,T=S+1;
    for(int i=1,e=0;i<=n;i++){
        scanf("%s",cc+1);
        for(int j=1;j<=m;j++){
            id[i][j]=++e;
            if(cc[j]=='#')
            add(id[i][j],id[i][j]+n*m,1);
            if(j==1||i==n)
            add(S,id[i][j],I);
            if(j==m||i==1)
            add(id[i][j]+n*m,T,I);
        }
    }
    for(int i=1;i<=n;i++)for(int j=1;j<=m;j++){
        for(int a=-2;a<=2;a++)for(int b=-2;b<=2;b++){
            int i_=i+a,j_=j+b;
            if(i_<=0||i_>n||j_<=0||j_>m)continue;
            if(a==0&&b==0)continue;
            add(id[i][j]+n*m,id[i_][j_],I);
        }
    }
    int ans=0;while(bfs())ans+=dfs(S,I);
    printf("%d",ans);return 0;
}