#include<bits/stdc++.h>
#define L(i, j, k) for(int i = (j); i <= (k); ++i)
#define R(i, j, k) for(int i = (j); i >= (k); --i)
#define ll long long
#define vi vector <int>
#define sz(a) ((int) (a).size())
#define me(f, x) memset(f, x, sizeof(f))
#define ull unsigned long long
#define pb emplace_back
using namespace std; 
const int N = 2507;
template < int N, int Ne >  struct flows { 
	using F = ll; // flow type
	F inf = 1e18;
	int n, s, t; // Remember to assign n, s and t !
	int ehd[N], cur[N], ev[Ne << 1], enx[Ne << 1], eid = 1;
	void clear() {
		eid = 1, memset(ehd, 0, sizeof(ehd));
	}
	F ew[Ne << 1], dis[N];
	void Eadd(int u, int v, F w) {
		++eid, enx[eid] = ehd[u], ew[eid] = w, ev[eid] = v, ehd[u] = eid;
	}
	void add(int u, int v, F w) {
		Eadd(u, v, w), Eadd(v, u, 0);
	}
	bool bfs() {
		queue < int > q;
		L(i, 1, n) dis[i] = inf, cur[i] = ehd[i]; 
		q.push(s), dis[s] = 0;
		while(!q.empty()) {
			int u = q.front();
			q.pop();
			for(int i = ehd[u]; i; i = enx[i]) if(ew[i] && dis[ev[i]] == inf) {
				dis[ev[i]] = dis[u] + 1, q.push(ev[i]);
			}
		}
		return dis[t] < inf;
	}
	F dfs(int x, F now) {
		if(!now || x == t) return now;
		F res = 0, f;
		for(int i = cur[x]; i; i = enx[i]) {
			cur[x] = i;
			if(ew[i] && dis[ev[i]] == dis[x] + 1) {
				f = dfs(ev[i], min(now, ew[i])), ew[i] -= f, now -= f, ew[i ^ 1] += f, res += f;
				if(!now) break;
			}
		}
		return res;
	}
	F max_flow() {
		F res = 0;
		while(bfs()) res += dfs(s, inf);
		return res;
	}
} ; 

flows < N * 50, N * 50 > F;
int n, m;
int a[57][57];
int P(int x, int y, int o) {
	return o * n * m + (x - 1) * m + y;
}
int main() {
	// freopen("data.txt","r",stdin);
	ios :: sync_with_stdio(false);
	cin.tie(0); cout.tie(0);
	cin >> n >> m;
	L(i, 1, n) {
		string s;
		cin >> s;
		L(j, 0, m - 1) {
			a[i][j + 1] = s[j] == '#';
		}
	}
	F.n = n * m * 2;
	F.s = ++F.n;
	F.t = ++F.n;
	int ans = 0;
	if(a[1][1])++ans,a[1][1]=0;
	if(a[n][m])++ans,a[n][m]=0;
	L(i, 2, m) if(a[1][i]) F.add(F.s, P(1, i, 0), 1);
	L(i, 1, n - 1) if(a[i][m]) F.add(F.s, P(i, m, 0), 1);
	L(i, 1, n) 
		L(j, 1, m) 
			if(a[i][j]) 
				F.add(P(i, j, 0), P(i, j, 1), 1);
	L(i, 2, n) if(a[i][1]) F.add(P(i, 1, 1), F.t, 1);
	L(i, 1, m - 1) if(a[n][i]) F.add(P(n, i, 1), F.t, 1);
	vector<pair<int,int>>dir;
	// dir.pb(0, 1);
	// dir.pb(0, -1);
	// dir.pb(1, 0);
	// dir.pb(1, 1);

	L(i, 1, n) {
		L(j, 1, m) if(a[i][j]) {
			L(d1, 0, 2) {
				L(d2, -2, 2) {
					int ni = i + d1;
					int nj = j + d2;
					if(1 <= ni && ni <= n && 1 <= nj && nj <= m && a[ni][nj]) {
						F.add(P(i, j, 1), P(ni, nj, 0), 1);
						F.add(P(ni, nj, 1), P(i, j, 0), 1);
					}
				}
			}
		}
	}
	cout << ans + F.max_flow() << '\n';
	return 0;
}