using System;
using System.Linq;
using System.Collections.Generic;
using Debug = System.Diagnostics.Debug;
using SB = System.Text.StringBuilder;
using System.Numerics;
using static System.Math;
using Point = System.Numerics.Complex;
using Number = System.Int64;
namespace Program {
    public class Solver {
        Random rnd = new Random(0);
        public void Solve() {
            var n = ri;
            var m = ri;
            var s = Enumerate(n, x => rs);
            var mf = new CompLib.Graph.Flow.MaxFlow(2 * n * m + 2);
            var src = 2 * n * m;
            var sink = src + 1;
            var all = n * m;
            const int inf = 1000000;
            var ans = 0;
            for (int i = 0; i < n; i++)
                for (int j = 0; j < m; j++)
                {
                    if (s[i][j] == '.') continue;
                    ans++;
                    var p = i * m + j;
                    //[][]
                    if (j + 1 < m && s[i][j + 1] == '#')
                    {
                        ans--;
                        var q = p + 1;
                        mf.AddDirectedEdge(src, p, 1);
                        mf.AddDirectedEdge(p, q + all, inf);
                        if (i != 0)
                            mf.AddDirectedEdge(p, q + all - m, inf);

                    }
                    mf.AddDirectedEdge(p, all + p, inf);
                    //[]
                    //[]
                    if (i + 1 < n && s[i + 1][j] == '#')
                    {
                        ans--;
                        var q = p + m;
                        mf.AddDirectedEdge(all + p, sink, 1);
                        mf.AddDirectedEdge(q, p + all, inf);
                        if (j != 0) mf.AddDirectedEdge(q - 1, p + all, inf);
                    }
                }
            /*
            for (int i = 0; i < mf.G.Length; i++)
                foreach (var e in mf.G[i])
                    if (e.Cap != 0)
                        Console.WriteLine($"{i} {e.To} {e.Cap}");
            */
            ans += mf.Execute(src, sink);
            Console.WriteLine(ans);

        }
        const long INF = 1L << 60;
        int ri { get { return sc.Integer(); } }
        long rl { get { return sc.Long(); } }
        double rd { get { return sc.Double(); } }
        string rs { get { return sc.Scan(); } }
        public IO.StreamScanner sc = new IO.StreamScanner(Console.OpenStandardInput());

        static T[] Enumerate<T>(int n, Func<int, T> f) {
            var a = new T[n];
            for (int i = 0; i < n; ++i) a[i] = f(i);
            return a;
        }
        static public void Swap<T>(ref T a, ref T b) { var tmp = a; a = b; b = tmp; }
    }
}

#region main
static class Ex {
    static public string AsString(this IEnumerable<char> ie) { return new string(ie.ToArray()); }
    static public string AsJoinedString<T>(this IEnumerable<T> ie, string st = " ") {
        return string.Join(st, ie);
    }
    static public void Main() {
        Console.SetOut(new Program.IO.Printer(Console.OpenStandardOutput()) { AutoFlush = false });
        var solver = new Program.Solver();
        solver.Solve();
        Console.Out.Flush();
    }
}
#endregion
#region Ex
namespace Program.IO {
    using System.IO;
    using System.Text;
    using System.Globalization;

    public class Printer: StreamWriter {
        public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } }
        public Printer(Stream stream) : base(stream, new UTF8Encoding(false, true)) { }
    }

    public class StreamScanner {
        public StreamScanner(Stream stream) { str = stream; }

        public readonly Stream str;
        private readonly byte[] buf = new byte[1024];
        private int len, ptr;
        public bool isEof = false;
        public bool IsEndOfStream { get { return isEof; } }

        private byte read() {
            if (isEof) return 0;
            if (ptr >= len)
            {
                ptr = 0;
                if ((len = str.Read(buf, 0, 1024)) <= 0)
                {
                    isEof = true;
                    return 0;
                }
            }
            return buf[ptr++];
        }

        public char Char() {
            byte b = 0;
            do b = read(); while ((b < 33 || 126 < b) && !isEof);
            return (char)b;
        }
        public string Scan() {
            var sb = new StringBuilder();
            for (var b = Char(); b >= 33 && b <= 126; b = (char)read()) sb.Append(b);
            return sb.ToString();
        }
        public string ScanLine() {
            var sb = new StringBuilder();
            for (var b = Char(); b != '\n' && b != 0; b = (char)read()) if (b != '\r') sb.Append(b);
            return sb.ToString();
        }
        public long Long() { return isEof ? long.MinValue : long.Parse(Scan()); }
        public int Integer() { return isEof ? int.MinValue : int.Parse(Scan()); }
        public double Double() { return isEof ? double.NaN : double.Parse(Scan(), CultureInfo.InvariantCulture); }
    }
}

#endregion

namespace CompLib.Graph.Flow {
    using C = System.Int32;
    #region Max Flow
    /// <summary>
    /// 辺の追加を行い，最大流を求めることが可能なグラフです．
    /// </summary>
    public class MaxFlow {
        public readonly List<Edge>[] G;
        readonly int[] lv, iter;
        /// <summary>
        /// 頂点数 <paramref name="V"/> で辺が存在しないグラフを構築します．
        /// </summary>
        /// <param name="V">頂点の数</param>
        /// <remarks>この操作は O(<paramref name="V"/>) で実行されます．</remarks>
        public MaxFlow(int V) {
            G = new List<Edge>[V];
            lv = new int[V];
            iter = new int[V];
            for (int i = 0; i < G.Length; i++)
                G[i] = new List<Edge>();
        }

        /// <summary>
        /// 頂点 <paramref name="from"/> から頂点 <paramref name="to"/> への容量 <paramref name="cap"/> の有向辺を追加します．
        /// </summary>
        /// <param name="from">始点となる頂点の 0-indexed での番号</param>
        /// <param name="to">終点となる頂点の 0-indexed での番号</param>
        /// <param name="cap">辺の容量</param>
        /// <remarks>この操作は O(1) で実行されます．</remarks>
        public void AddDirectedEdge(int from, int to, C cap) {
            addEdge(from, to, cap, 0);
        }

        /// <summary>
        /// 頂点 <paramref name="from"/> から頂点 <paramref name="to"/> への容量 <paramref name="cap"/> の無向辺を追加します．
        /// </summary>
        /// <param name="from">始点となる頂点の 0-indexed での番号</param>
        /// <param name="to">終点となる頂点の 0-indexed での番号</param>
        /// <param name="cap">辺の容量</param>
        /// <remarks>この操作は O(1) で実行されます．</remarks>
        public void AddUndirectedEdge(int from, int to, C cap) {
            addEdge(from, to, cap, cap);
        }
        void addEdge(int f, int t, C c1, C c2) {
            var a = new Edge(t, c1);
            var b = new Edge(f, c2);
            Edge.Link(a, b);
            G[f].Add(a);
            G[t].Add(b);
        }


        /// <summary>
        /// 頂点 <paramref name="src"/> から頂点 <paramref name="sink"/> へ最大で流量 <paramref name="f"/> だけフローを流します．
        /// </summary>
        /// <param name="src">ソースとなる頂点の 0-indexed での番号</param>
        /// <param name="sink">シンクとなる頂点の 0-indexed での番号</param>
        /// <param name="f">ソースからシンクへと流す最大の容量．-1を指定した場合，最大流を求める．</param>
        /// <remarks>この操作はDinic法に基づき，最悪計算量 O(EV^2) で実行されます．Vは頂点の数，Eは辺の数ｗ表します．</remarks>
        public C Execute(int src, int sink, C f = -1) {
            C flow = 0;
            if (f < 0) f = C.MaxValue;
            while (f > 0)
            {
                bfs(src);
                if (lv[sink] == 0) return flow;
                Array.Clear(iter, 0, iter.Length);
                C df;
                while ((df = dfs(src, sink, f)) > 0) { flow += df; f -= df; }
            }
            return flow;
        }

        void bfs(int s) {
            Array.Clear(lv, 0, lv.Length);
            var q = new Queue<int>();
            lv[s] = 1;
            q.Enqueue(s);
            while (q.Count > 0)
            {
                var v = q.Dequeue();
                foreach (var e in G[v])
                    if (e.Cap > 0 && lv[e.To] == 0)
                    {
                        lv[e.To] = lv[v] + 1;
                        q.Enqueue(e.To);
                    }
            }

        }
        C dfs(int v, int t, C f) {
            if (v == t) return f;
            C ret = 0;
            for (; iter[v] < G[v].Count; iter[v]++)
            {
                var e = G[v][iter[v]];
                if (e.Cap <= 0 || lv[v] >= lv[e.To]) continue;
                C df = dfs(e.To, t, Math.Min(f, e.Cap));
                if (df <= 0) continue;
                e.Cap -= df;
                e.Rev.Cap += df;
                ret += df; f -= df;
                if (f == 0) break;
            }
            return ret;

        }
        public class Edge {
            public static void Link(Edge e1, Edge e2) {
                e1.Rev = e2; e2.Rev = e1;
            }
            public int To { get; private set; }
            public Edge Rev { get; private set; }
            public C Cap { get; set; }
            public Edge(int t, C c) {
                To = t;
                Cap = c;
            }
            public override string ToString() {
                return string.Format("to: {0}, cap: {1}", To, Cap);
            }
        }


    }
    #endregion
}



Measured memory_bytes: 18320