/*FreeTimeLove's code.
Love has a nasty habit of disappearing over night.*/
#include<bits/stdc++.h>
namespace FRTMLV{
#define ll long long
#define LD long double
#define i7 __int128
#define re return
#define con continue
using namespace std;
template<class T>inline bool ckmin(T &a,T b){re b<a?a=b,1:0;}
template<class T>inline bool ckmax(T &a,T b){re a<b?a=b,1:0;}
const int N=5e3+5;
inline int rd(){
	int ans=0,f=0;
	char ch=getchar();
	while(ch<'0'||ch>'9')f^=(ch=='-'),ch=getchar();
	while(ch>='0'&&ch<='9')ans=(ans<<3)+(ans<<1)+(ch^48),ch=getchar();
	re f?-ans:ans;
}
const int INF=0x3f3f3f3f;
int n,m;
char s[55][55];
namespace DNC{
	int s,t;
	int nd[N],nds[N],tt=1;
	int d[N];
	struct edge{int v,w,nxt;}e[N*50];
	void add(int u,int v,int w){e[++tt]={v,w,nd[u]};nd[u]=tt;}
	void adds(int u,int v,int w){add(u,v,w),add(v,u,0);}
	bool bfs(){
		memset(d,0x3f,sizeof d),d[s]=0;
		queue<int>q;q.push(s);
		while(q.size()){
			int u=q.front();q.pop();
			nds[u]=nd[u];
			for(int i=nd[u];i;i=e[i].nxt){
				int v=e[i].v;
				if(e[i].w&&d[v]==INF)d[v]=d[u]+1,q.push(v);
			}
		}
		re d[t]<INF;
	}
	int dfs(int u,int flw){
		if(u==t)re flw;
		int ret=0,x;
		for(int &i=nds[u];i;i=e[i].nxt){
			int v=e[i].v;
			if(!e[i].w||d[v]!=d[u]+1)con;
			x=dfs(v,min(e[i].w,flw));
			if(x){
				flw-=x,ret+=x;
				e[i].w-=x,e[i^1].w+=x;
				if(!flw)break;
			}
		}
		re ret;
	}
	int dinic(){
		int flw=0;
		while(bfs())flw+=dfs(s,INF);
		re flw;
	}
}
#define inc(i,j) (m*(i-1)+j)
int main(){
	n=rd(),m=rd();
	for(int i=1;i<=n;i++)scanf("%s",s[i]+1);
	DNC::s=n*m*2+1,DNC::t=DNC::s+1;
	for(int i=1;i<=n;i++)
	for(int j=1;j<=m;j++){
		DNC::adds(inc(i,j),inc(i,j)+n*m,s[i][j]=='#');
		for(int x=-2;x<=2;x++)
		for(int y=-2;y<=2;y++){
			int nx=i+x,ny=j+y;
			if(nx<1||nx>n||ny<1||ny>m)con;
			if(!x&&!y)con;
			DNC::adds(inc(i,j)+n*m,inc(nx,ny),INF);
		}
		if(i==n||j==1)DNC::adds(DNC::s,inc(i,j),INF);
		if(i==1||j==m)DNC::adds(inc(i,j)+n*m,DNC::t,INF);
	}
	printf("%d\n",DNC::dinic());
	re 0;
}
/*
4 4
.###
#...
#.#.
#...

4 6
.##...
.#....
##....
....#.

*/
}int main(){re FRTMLV::main();}