#include <bits/stdc++.h>
struct Flow {
static constexpr int INF = 1e9;
int n;
struct Edge {
int to, cap;
Edge(int to, int cap) : to(to), cap(cap) {}
};
std::vector<Edge> e;
std::vector<std::vector<int>> g;
std::vector<int> cur, h;
Flow(int n) : n(n), g(n) {}
bool bfs(int s, int t) {
h.assign(n, -1);
std::queue<int> que;
h[s] = 0;
que.push(s);
while (!que.empty()) {
int u = que.front();
que.pop();
for (int i : g[u]) {
auto [v, c] = e[i];
if (c > 0 && h[v] == -1) {
h[v] = h[u] + 1;
if (v == t)
return true;
que.push(v);
}
}
}
return false;
}
int dfs(int u, int t, int f) {
if (u == t)
return f;
int r = f;
for (int &i = cur[u]; i < int(g[u].size()); ++i) {
int j = g[u][i];
auto [v, c] = e[j];
if (c > 0 && h[v] == h[u] + 1) {
int a = dfs(v, t, std::min(r, c));
e[j].cap -= a;
e[j ^ 1].cap += a;
r -= a;
if (r == 0)
return f;
}
}
return f - r;
}
void addEdge(int u, int v, int c) {
g[u].push_back(e.size());
e.emplace_back(v, c);
g[v].push_back(e.size());
e.emplace_back(u, 0);
}
int maxFlow(int s, int t) {
int ans = 0;
while (bfs(s, t)) {
cur.assign(n, 0);
ans += dfs(s, t, INF);
}
return ans;
}
};int main() {
std::ios::sync_with_stdio(false);
std::cin.tie(nullptr);
int n, m;
std::cin >> n >> m;
std::vector<std::string> s(n);
for (int i = 0; i < n; ++i)
std::cin >> s[i];
Flow flow(2 * n * m + 2);
int S = 2 * n * m, T = S + 1;
int ans = 0;
for (int i = 0; i < n; ++i) {
for (int j = 0; j < m; ++j) {
if (s[i][j] == '.')
continue;
++ans;
std::vector<int> v, h;
if (i < n - 1 && s[i + 1][j] == '#')
v.push_back(i * m + j), --ans;
if (j < m - 1 && s[i][j + 1] == '#')
h.push_back(i * m + j), --ans;
if (i && s[i - 1][j] == '#')
v.push_back((i - 1) * m + j);
if (j && s[i][j - 1] == '#')
h.push_back(i * m + j - 1);
for (auto x : v)
for (auto y : h)
flow.addEdge(x, y + n * m, 1);
}
}
for (int i = 0; i < n * m; ++i) {
flow.addEdge(S, i, 1);
flow.addEdge(i + n * m, T, 1);
}
std::cout << ans + flow.maxFlow(S, T) << "\n";
return 0;
}
