#include <bits/stdc++.h>
#include <sys/types.h>
#include <unistd.h>

#define _overload(_1,_2,_3,name,...) name
#define _rep(i,n) _range(i,0,n)
#define _range(i,a,b) for(int i=int(a);i<int(b);++i)
#define rep(...) _overload(__VA_ARGS__,_range,_rep,)(__VA_ARGS__)

#define _rrep(i,n) _rrange(i,n,0)
#define _rrange(i,a,b) for(int i=int(a)-1;i>=int(b);--i)
#define rrep(...) _overload(__VA_ARGS__,_rrange,_rrep,)(__VA_ARGS__)

#define _all(arg) begin(arg),end(arg)
#define uniq(arg) sort(_all(arg)),(arg).erase(unique(_all(arg)),end(arg))
#define getidx(ary,key) lower_bound(_all(ary),key)-begin(ary)
#define clr(a,b) memset((a),(b),sizeof(a))
#define bit(n) (1LL<<(n))
#define popcount(n) (__builtin_popcountll(n))

using namespace std;

template<class T>bool chmax(T &a, const T &b) { return (a<b)?(a=b,1):0;}
template<class T>bool chmin(T &a, const T &b) { return (b<a)?(a=b,1):0;}

using ll=long long;
using R=long double;
const R EPS=1e-9L; // [-1000,1000]->EPS=1e-8 [-10000,10000]->EPS=1e-7
inline int sgn(const R& r){return(r > EPS)-(r < -EPS);}
inline R sq(R x){return sqrt(max(x,0.0L));}

const int dx[8]={1,0,-1,0,1,-1,-1,1};
const int dy[8]={0,1,0,-1,1,1,-1,-1};

const pid_t pid = getpid();

//Appropriately Changed
using W = ll;
using edge = struct {int to, rev; W cap, flow;};
using G = vector<vector<edge>>;

//Appropriately Changed
void add_edge(G &graph, int from, int to, W cap) {
	graph[from].push_back({to, int(graph[to].size()) , cap , 0});
	graph[to].push_back({from, int(graph[from].size()) - 1, 0 , 0});
}

W dinic(G &graph, int s, int t) {
	const W inf = 1LL << 50;
	const int n = graph.size();
	vector<int> level(n), iter(n);

	auto bfs = [&](int s, int t) {
		fill(begin(level), end(level), -1);
		queue<int> q;
		level[s] = 0, q.push(s);

		while (!q.empty()) {
			int v = q.front(); q.pop();
			for (auto &e : graph[v]) {
				if (level[e.to] == - 1 and e.cap > e.flow) {
					level[e.to] = level[v] + 1;
					q.push(e.to);
				}
			}
		}
		return (level[t] !=  -1);
	};

	auto dfs = [&](int v, int t, W f) {
		auto func = [&](int v, int t, W f, auto func)->W{

			if (v == t) return f;
			for (int &i = iter[v]; i < graph[v].size(); i++) {
				edge &e = graph[v][i];

				if (e.cap > e.flow and level[v] < level[e.to]) {

					W d = func(e.to, t, min(f, e.cap - e.flow), func);

					if (d > 0) {
						e.flow += d, graph[e.to][e.rev].flow -= d;
						return d;
					}
				}
			}

			return 0;
		};
		return func(v, t, f, func);
	};

	while (bfs(s, t)) {
		fill(begin(iter), end(iter), 0);
		while (dfs(s, t, inf) != 0 );
	}

	W ret = 0;
	for (auto &e : graph[s]) ret += e.flow;
	return ret;
}


char board[30][30];

int main(void){
	int r,c;
	cin >> r >> c;
	rep(i,r)rep(j,c) cin >> board[i][j];

	const int offset = (r - 1) * c;
	const int s = (r - 1) * c + r * (c - 1);
	const int t = s + 1;
	const int all = t + 1;

	G graph(all);
	const ll inf = 1LL << 20;
	int n = 0, m = 0;

	rep(i,r)rep(j,c) n += (board[i][j] == '#'); 

	rep(i,r-1)rep(j,c){
		if(board[i][j] != '#' or board[i+1][j] !='#') continue;
		const int idx = c * i + j;
		add_edge(graph,s,idx,0);
		add_edge(graph,idx,t,1);
		m++;
	}

	rep(i,r)rep(j,c-1){
		if(board[i][j] != '#' or board[i][j+1] !='#') continue;
		const int idx = (c - 1) * i + j + offset;
		add_edge(graph,s,idx,1);
		add_edge(graph,idx,t,0);
		m++;
	}

	rep(i,r-1)rep(j,c){
		if(board[i][j] != '#' or board[i+1][j] !='#') continue;
		const int idx = c * i + j;
		
		rep(k,r)rep(l,c-1){
			if(i != k and i+1 != k) continue;
			if(j != l and j != l+1) continue;
			if(board[k][l] != '#' or board[k][l+1] !='#') continue;

			const int idx2 = (c - 1) * k + l + offset;
			add_edge(graph,idx2,idx,inf);
		}
	}

	cout << n -  m + dinic(graph,s,t) << endl;
	return 0;
}


Measured memory_bytes: 3368