#include <bits/stdc++.h>
using namespace std;
const int inf = 1 << 30;
const long long linf = 1LL << 62;
const int MAX = 1020000;
long long dy[8] = {0, -1, 0, 1, 1, -1, 1, -1};
long long dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
const double pi = acos(-1);
const double eps = 1e-7;
template <typename T1, typename T2>
inline bool chmin(T1 &a, T2 b) {
  if (a > b) {
    a = b;
    return true;
  } else
    return false;
}
template <typename T1, typename T2>
inline bool chmax(T1 &a, T2 b) {
  if (a < b) {
    a = b;
    return true;
  } else
    return false;
}
template <typename T>
inline void print(T &a) {
  for (long long i = 0; i < (a.size()); i++) cout << a[i] << " ";
  cout << "\n";
}
template <typename T1, typename T2>
inline void print2(T1 a, T2 b) {
  cout << a << " " << b << "\n";
}
template <typename T1, typename T2, typename T3>
inline void print3(T1 a, T2 b, T3 c) {
  cout << a << " " << b << " " << c << "\n";
}
long long pcount(long long x) { return __builtin_popcountll(x); }
const long long mod = 1e9 + 7;
struct Dinic {
  struct edge {
    long long to, cap, rev;
  };
  vector<vector<edge>> G;
  vector<int> level, itr;
  long long n;
  const long long INF = 1 << 30;
  Dinic(long long n) : n(n) {
    G.resize(n);
    level.resize(n);
    itr.resize(n);
  }
  void add_edge(long long from, long long to, long long cap) {
    G[from].push_back({to, cap, (long long)G[to].size()});
    G[to].push_back({from, 0, (long long)G[from].size() - 1});
  }
  void bfs(int s) {
    fill(level.begin(), level.end(), -1);
    queue<int> q;
    level[s] = 0;
    q.push(s);
    while (!q.empty()) {
      int u = q.front();
      q.pop();
      for (auto &e : G[u]) {
        if (e.cap > 0 && level[e.to] < 0) {
          level[e.to] = level[u] + 1;
          q.push(e.to);
        }
      }
    }
  }
  long long dfs(int u, int t, long long f) {
    if (u == t) return f;
    for (int &i = itr[u]; i < G[u].size(); i++) {
      edge &e = G[u][i];
      if (e.cap > 0 && level[u] < level[e.to]) {
        long long d = dfs(e.to, t, min(f, e.cap));
        if (d > 0) {
          e.cap -= d;
          G[e.to][e.rev].cap += d;
          return d;
        }
      }
    }
    return 0;
  }
  long long max_flow(long long s, long long t) {
    long long flow = 0;
    while (1) {
      bfs(s);
      if (level[t] < 0) return flow;
      fill(itr.begin(), itr.end(), 0);
      long long f;
      while ((f = dfs(s, t, INF)) > 0) {
        flow += f;
      }
    }
  }
};
bool in(long long y, long long x, long long h, long long w) {
  return 0 <= y && y < h && 0 <= x && x < w;
}
void solve() {
  int h, w;
  cin >> h >> w;
  vector<string> s(h);
  for (long long i = 0; i < (h); i++) cin >> s[i];
  Dinic flow(4 * h * w);
  int S = 4 * h * w - 2, T = 4 * h * w - 1;
  int W = 2 * w - 1;
  set<int> se;
  int cnt = 0;
  int edge = 0;
  auto add = [&](int from, int to, int cap = 1) {
    edge++;
    flow.add_edge(from, to, cap);
    if (!se.count(from)) flow.add_edge(S, from, cap);
    if (!se.count(to)) flow.add_edge(to, T, cap);
    se.insert(from);
    se.insert(to);
  };
  for (long long i = 0; i < (h); i++)
    for (long long j = 0; j < (w); j++)
      if (s[i][j] == '#') cnt++;
  for (long long i = 0; i < (h - 1); i++)
    for (long long j = 0; j < (w); j++) {
      if (s[i][j] == '.') continue;
      if (j + 1 < w) {
        if (s[i + 1][j] == '#' && s[i][j + 1] == '#') {
          int from = (2 * i + 1) * W + 2 * j, to = 2 * i * W + 2 * j + 1;
          add(from, to);
        }
        if (s[i + 1][j] == '#' && s[i + 1][j + 1] == '#') {
          int from = (2 * i + 1) * W + 2 * j, to = 2 * (i + 1) * W + 2 * j + 1;
          add(from, to);
        }
      }
      if (j > 0) {
        if (s[i + 1][j] == '#' && s[i + 1][j - 1] == '#') {
          int from = (2 * i + 1) * W + 2 * j, to = 2 * (i + 1) * W + 2 * j - 1;
          add(from, to);
        }
        if (s[i][j - 1] == '#' && s[i + 1][j] == '#') {
          int from = (2 * i + 1) * W + 2 * j, to = 2 * i * W + 2 * j - 1;
          add(from, to);
        }
      }
    }
  for (long long i = 0; i < (h); i++) {
    for (long long j = 0; j < (w); j++) {
      if (j + 1 < w && s[i][j] == '#' && s[i][j + 1] == '#') {
        se.insert(2 * i * W + 2 * j + 1);
      }
      if (i + 1 < h && s[i][j] == '#' && s[i + 1][j] == '#') {
        se.insert((2 * i + 1) * W + 2 * j);
      }
    }
  }
  cout << cnt - (se.size() - flow.max_flow(S, T)) << "\n";
}
int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  int t = 1;
  while (t--) {
    solve();
  }
}
