#include <bits/stdc++.h>
using namespace std;
const int N = 50 * 50 * 50;
namespace dinic {
struct edge {
    int v, p;
    long long c;
};
vector<edge> g[N];
int n;
int dis[N], cur[N];
int addv(int cnt = 1) {
    while (cnt--) g[n++].clear();
    return n - 1;
}
void adde(int u, int v, long long c) {
    g[u].push_back({v, (int)g[v].size(), c});
    g[v].push_back({u, (int)g[u].size() - 1, 0});
}
bool bfs(int s, int t) {
    fill_n(dis, n, INT_MAX);
    queue<int> q;
    q.push(t);
    dis[t] = 0;
    while (!q.empty()) {
        int u = q.front();
        q.pop();
        for (const edge& e : g[u]) {
            int v = e.v;
            if (dis[v] != INT_MAX || !g[e.v][e.p].c) continue;
            dis[v] = dis[u] + 1;
            q.push(v);
        }
    }
    return dis[s] != INT_MAX;
}
long long dfs(int u, int t, long long f) {
    if (u == t) return f;
    long long sf = 0;
    for (int& i = cur[u]; i != g[u].size(); ++i) {
        edge& e = g[u][i];
        int v = e.v;
        if (!e.c || dis[v] + 1 != dis[u]) continue;
        long long df = dfs(v, t, min(e.c, f));
        sf += df;
        f -= df;
        e.c -= df;
        g[v][e.p].c += df;
        if (!f) break;
    }
    return sf;
}
long long dinic(int s, int t, long long mf) {
    long long sf = 0;
    while (bfs(s, t)) {
        fill_n(cur, n, 0);
        long long f = dfs(s, t, mf);
        sf += f;
        mf -= f;
        if (!mf) break;
    }
    return sf;
}
};  // namespace dinic

string mp[55];

int id[55][55];
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int n, m;
    cin >> n >> m;
    for (int i = 0; i < n; ++i) cin >> mp[i];
    dinic::n = 2 * n * m + 3;
    int s = 2 * n * m + 1, t = s + 1;
    int cnt = 0;
    for (int i = 0; i < n; ++i)
        for (int j = 0; j < m; ++j) {
            id[i][j] = ++cnt;
            if (mp[i][j] == '#') dinic::adde(id[i][j], id[i][j] + m * n, 1);
            if (j == 0 || i == n - 1) {
                dinic::adde(s, id[i][j], 0x3f3f3f3f);
            }
            if (i == 0 || j == m - 1) {
                dinic::adde(n * m + id[i][j], t, 0x3f3f3f3f);
            }
        }
    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) {
                    int xx = i + dx, yy = j + dy;
                    if (xx < 0 || xx >= n || yy < 0 || yy >= m) continue;
                    if (dx == 0 && dy == 0) continue;
                    dinic::adde(id[i][j] + n * m, id[xx][yy], 0x3f3f3f3f);
                }
            }
        }
    }
    cout << dinic::dinic(s, t, 0x3f3f3f3f) << endl;
}