#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using vi = vector<int>;
using vl = vector<ll>;
constexpr ll INF = 1e9 + 7;
#define rep(i, l, r) for(int i =l;i < r;++i)
#define sz(c) (int)c.size()


struct Dinic {
    struct Edge {
        int to, rev;
        ll c, oc;

        ll flow() { return max(oc - c, 0LL); } // if you need flows
    };

    vi lvl, ptr, q;
    vector<vector<Edge>> adj;

    Dinic(int n) : lvl(n), ptr(n), q(n), adj(n) {}

    void addEdge(int a, int b, ll c, ll rcap = 0) {
        adj[a].push_back({b, sz(adj[b]), c, c});
        adj[b].push_back({a, sz(adj[a]) - 1, rcap, rcap});
    }

    ll dfs(int v, int t, ll f) {
        if (v == t || !f) return f;
        for (int &i = ptr[v]; i < sz(adj[v]); i++) {
            Edge &e = adj[v][i];
            if (lvl[e.to] == lvl[v] + 1)
                if (ll p = dfs(e.to, t, min(f, e.c))) {
                    e.c -= p, adj[e.to][e.rev].c += p;
                    return p;
                }
        }
        return 0;
    }

    ll calc(int s, int t) {
        ll flow = 0;
        q[0] = s;
        rep(L, 0, 31) do { // 'int L=30' maybe faster for random data
                lvl = ptr = vi(sz(q));
                int qi = 0, qe = lvl[s] = 1;
                while (qi < qe && !lvl[t]) {
                    int v = q[qi++];
                    for (Edge e: adj[v])
                        if (!lvl[e.to] && e.c >> (30 - L))
                            q[qe++] = e.to, lvl[e.to] = lvl[v] + 1;
                }
                while (ll p = dfs(s, t, LLONG_MAX)) flow += p;
            } while (lvl[t]);
        return flow;
    }

    bool leftOfMinCut(int a) { return lvl[a] != 0; }
};


int main() {
    cin.tie(0)->sync_with_stdio(false);
    int n, m;
    cin >> n >> m;
    int N = n * m * 2 + 2;
    int st = N - 2, en = N - 1;
    int cur = 0;
    Dinic sol(N);
    vector<vector<int>> who(n, vector<int>(m));
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < m; ++j) {
            char c;
            cin >> c;
            who[i][j] = cur;
            sol.addEdge(cur, cur + 1, c == '#');
            if (!j || i == n - 1)sol.addEdge(st, cur, INF);
            if (!i || j == m - 1)sol.addEdge(cur + 1, en, INF);
            cur += 2;
        }
    }
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < m; ++j) {
            for (int dx = -2; dx <= 2; ++dx) {
                for (int dy = -2; dy <= 2; ++dy) {
                    if (abs(dx) + abs(dy) > 3 || abs(dx) + abs(dy) == 0)continue;
                    int ni = i + dx, nj = j + dy;
                    if (ni >= 0 && ni < n && nj >= 0 && nj < m) {
                        sol.addEdge(who[i][j] + 1, who[ni][nj], INF);
                    }
                }
            }
        }
    }
    cout << sol.calc(st,en);
}