using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using static System.Console;
using static System.Math;
 
public class Hello{
    static public int mod = 1000000007;
    public static void Main(){
        // 方針
        // 
        int[] num = inta();
        char[,] map = new char[num[0]+1,num[1]+1];
        for(int i=0;i<num[0];i++){
            string temp = rstr();
            for(int j=0;j<num[1];j++){
                map[i,j] = temp[j];
            }
        }
        int[,] count = new int[num[0]+1,num[1]+1];
        for(int i=0;i<num[0];i++){
            for(int j=0;j<num[1];j++){
                count[i,j] = 99999999;
            }
        }
        count[0,0] = 0;
        if(map[0,0] == '#'){
            count[0,0]++;
        }
        for(int i=0;i<num[0];i++){
            for(int j=0;j<num[1];j++){
                    /*
                    for(int q=0;q<num[0];q++){
                        for(int w=0;w<num[1];w++){
                            Write(count[q,w]);
                            Write(" ");
                        }
                        WriteLine();
                    }
                    */
                if(map[i,j] == '.'){
                    if(map[i,j+1] == '#'){
                        count[i,j+1] = Min(count[i,j+1],count[i,j]+1);
                    }else{
                        count[i,j+1] = Min(count[i,j+1],count[i,j]);
                    }
                    if(map[i+1,j] == '#'){
                        count[i+1,j] = Min(count[i+1,j],count[i,j]+1);
                    }else{
                        count[i+1,j] = Min(count[i+1,j],count[i,j]);
                    }
                }else{
                    count[i,j+1] = Min(count[i,j+1],count[i,j]);
                    count[i+1,j] = Min(count[i+1,j],count[i,j]);
                }
            }
        }
        WriteLine(count[num[0]-1,num[1]-1]);
        /*
        for(int i=0;i<num[0];i++){
            for(int j=0;j<num[1];j++){
                Write(count[i,j]);
                Write(" ");
            }
            WriteLine();
        }
        */
        
        
    }
    static int ncr(int n,int r){r = Min(r,n-r);long nn = 1;for(int i=n-r+1;i<=n;i++){nn = nn*i%mod;}long rr = 1;for(int i=1;i<=r;i++){rr = rr*i%mod;}rr = square((int)rr,mod-2);nn = nn * rr %mod;return (int)nn;}
    // a^b mod
    static int square(int a,int b){string binary = Convert.ToString(b,2);int bileng = binary.Length;long a_power = a;long value = 1;for(int i=bileng-1;i>=0;i--){if(binary[i] == '1'){value = value*a_power%mod;}a_power = a_power*a_power%mod;}return (int)value;}
    //static int square2(long a,long b,long m){var list = new List<int>();int temp = 1;long n2 = a;list.Add(1);int count = 1;while(temp < b){list.Add((int)n2);temp*=2;count++;n2 = n2*n2%m;}long ret = 1;while(b > 0){if(temp <= b){b -= temp;ret = ret*list[count]%1000000007;}count--;temp/=2;}return(int)ret;}
    //各種読取
    static string rstr(){ return ReadLine(); }
    static int rint(){ return int.Parse(ReadLine()); }
    static long rlong(){ return long.Parse(ReadLine()); }
    static string[] stra(){ return ReadLine().Split(' '); }
    static int[] inta(){ string[] read_str_array = ReadLine().Split(' '); int[] return_int_array = new int[read_str_array.Length]; for(int countup_i=0;countup_i<read_str_array.Length;countup_i++){ return_int_array[countup_i] = int.Parse(read_str_array[countup_i]); } return return_int_array; }
    static int[,] inta2(int num_array,int in_array){ int[,] int_array2 = new int[num_array,in_array]; for(int i=0;i<num_array;i++){ int[] temp_array = inta(); for(int j=0;j<in_array;j++){ int_array2[i,j] = temp_array[j]; } } return int_array2; }
    static long[] longa(){ string[] read_str_array = ReadLine().Split(' '); long[] return_long_array = new long[read_str_array.Length]; for(long countup_i=0;countup_i<read_str_array.Length;countup_i++){ return_long_array[countup_i] = long.Parse(read_str_array[countup_i]); } return return_long_array; }
    static double[] doublea(){ string[] read_str_array = ReadLine().Split(' '); double[] return_double_array = new double[read_str_array.Length]; for(long countup_i=0;countup_i<read_str_array.Length;countup_i++){ return_double_array[countup_i] = long.Parse(read_str_array[countup_i]); } return return_double_array; }
    // -----------------------------
    static long divideup(long divided,long divid){ long temp_divide = divided/divid; if(divided % divid > 0){ temp_divide++; } return temp_divide; }
    static long GCD(long a,long b){ if(a < b){ long temp = a; a = b; b = temp; } if(a % b == 0){ return b; } else{ long temp = b; b = a%b; a = temp; return GCD(a,b); } }
    static long LCM(long a,long b){ return a * b / GCD(a,b); }
}



//知見
// (string) hogestr -> (char[]) hoge
    // char hoge = hogestr.ToCharArray();
// (char[]) hoge -> (string) hogestr

Measured memory_bytes: 13200