/*
    Author:zeke
    
    pass System Test!
    GET AC!!
*/
#include <iostream>
#include <queue>
#include <vector>
#include <iostream>
#include <vector>
#include <string>
#include <cassert>
#include <algorithm>
#include <functional>
#include <cmath>
#include <queue>
#include <set>
#include <stack>
#include <deque>
#include <map>
#include <iomanip>
#include <utility>
#include <stack>
#include <bitset>
using ll = long long;
using ld = long double;
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define all(x) (x).begin(), (x).end()
#define rep3(var, min, max) for (ll(var) = (min); (var) < (max); ++(var))
#define repi3(var, min, max) for (ll(var) = (max)-1; (var) + 1 > (min); --(var))
#define Mp(a, b) make_pair((a), (b))
#define F first
#define S second
#define Icin(s) \
    ll(s);      \
    cin >> (s);
#define Scin(s) \
    ll(s);      \
    cin >> (s);
template <class T>
bool chmax(T &a, const T &b)
{
    if (a < b)
    {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
bool chmin(T &a, const T &b)
{
    if (b < a)
    {
        a = b;
        return 1;
    }
    return 0;
}
typedef pair<ll, ll> P;
typedef vector<ll> V;
typedef vector<V> VV;
typedef vector<P> VP;
ll mod = 1e9 + 7;
ll MOD = 1e9 + 7;
//ll INF = 1e18;
#define int ll
const ll INF = 1e18;
typedef int Weight;
struct Edge {  //src:辺の始点,dst:辺の終点,weight:辺の重さ
  int src, dst;
  Weight weight;
  Edge(int src, int dst, Weight weight) :
    src(src), dst(dst), weight(weight) { }
};
bool operator < (const Edge &e, const Edge &f) {
  return e.weight != f.weight ? e.weight > f.weight : //辺は重さが重いものを"小さい"と定義する
    e.src != f.src ? e.src < f.src : e.dst < f.dst;
}
typedef vector<Edge> Edges;
typedef vector<Edges> Graph;
//引数 g:隣接リスト,s:始点,dist:各頂点までの距離が入る,prev:最短路木の親頂点が入る
//戻値 なし
void shortestPath(const Graph &g,int s,vector<Weight> &dist,vector<int> &prev) {
  int n = g.size();
  dist.assign(n, INF); dist[s] = 0;
  prev.assign(n, -1);
  priority_queue<Edge> Q;
  Q.push(Edge(-2, s, 0));
  while(!Q.empty()) {
    Edge e = Q.top(); Q.pop();
    if (prev[e.dst] != -1) continue;
    prev[e.dst] = e.src;
    for(auto f=g[e.dst].begin();f!=g[e.dst].end();f++){
      if (dist[f->dst] > e.weight+f->weight) {
        dist[f->dst] = e.weight+f->weight;
        Q.push(Edge(f->src, f->dst, e.weight+f->weight));
      }
    }
  }
}

//引数 prev:最短路木の親頂点集合,t:終点
//戻値 path:sからtへの最短経路
vector<int> buildPath(const vector<int> &prev, int t) {
  vector<int> path;
  for (int u = t; u >= 0; u = prev[u])
    path.push_back(u);
  reverse(path.begin(), path.end());
  return path;
}
/*int main(){
  // ...
  Graph g(v);    //頂点数vの空隣接リストgを生成
  // ...
  g[s].push_back(Edge(s,t,w));    //隣接リストgにsからtに向かう重さwの辺を追加
  // ...
  vector<Weight> dist;
  vector<int> prev;
  shortestPath(g,0,dist,prev);
  // ...
}*/
signed main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll h,w;
    cin>>h>>w;
    VV vec(h,V(w,-1));
    Graph g(h*w);
    rep(i,h){
        string s;
        cin>>s;
        rep(j,w){
            if(s[j]=='.'){
                vec[i][j]=1;
            }else{
                vec[i][j]=0;
            }
        }
    }
        /*  rep(i,h){
        rep(j,w){
            cout<<vec[i][j];
        }
        cout<<endl;
    }*/
  //  cout<<"h"<<endl;
    rep(i,h){
        rep(j,w){
            int dx[]={0,1};
            int dy[]={1,0};
            rep(k,2){
                if(i+dy[k]<h&&j+dx[k]<w){
                    ll base=i*w+j;
                    ll to=(i+dy[k])*w+(j+dx[k]);
                    if(vec[i+dy[k]][j+dx[k]]==0){
                        if(vec[i][j]==1){
                            g[base].push_back(Edge(base,to,1));
                        }else{
                            g[base].push_back(Edge(base,to,0));
                        }
                    }else{
                        g[base].push_back(Edge(base,to,0));
                    }
                }
            }
        }
    }
    vector<Weight> dist;
    vector<int> prev;
    shortestPath(g,0,dist,prev);
 /*   rep(i,h){
        rep(j,w){
            cout<<g[i*h+j].size()<<" ";
        }
        cout<<endl;
    }*/
   // cout<<endl;
    ll res=dist[h*w-1];
    if(vec[0][0]==0){
        res++;
    }
    cout<<res<<endl;
}


Measured memory_bytes: 1408