#include <bits/stdc++.h>
using namespace std;

#define int long long
 
#define rep(i,n) for(int i=0, i##_len=(n); i<i##_len; ++i)

#define YES puts("YES")
#define Yes puts("Yes")
#define NO  puts("NO")
#define No  puts("No")
#define ALL(v) (v).begin(), (v).end()
int gcd(int a, int b) { return b ? gcd(b, a % b) : a; }
 
 
 
#if 1
//-------------
// DUMPマクロ
// https://www.creativ.xyz/dump-cpp-652/

#define repi(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)

// vector
template <typename T>
istream& operator>>(istream& is, vector<T>& vec) {
    for (T& x : vec) is >> x;
    return is;
}
// pair
template <typename T, typename U>
ostream& operator<<(ostream& os, pair<T, U>& pair_var) {
    os << "(" << pair_var.first << ", " << pair_var.second << ")";
    return os;
}
// vector
template <typename T>
ostream& operator<<(ostream& os, const vector<T>& vec) {
    os << "{";
    for (int i = 0; i < vec.size(); i++) {
        os << vec[i] << (i + 1 == vec.size() ? "" : ", ");
    }
    os << "}";
    return os;
}
// map
template <typename T, typename U>
ostream& operator<<(ostream& os, map<T, U>& map_var) {
    os << "{";
    repi(itr, map_var) {
        os << *itr;
        itr++;
        if (itr != map_var.end()) os << ", ";
        itr--;
    }
    os << "}";
    return os;
}
// set
template <typename T>
ostream& operator<<(ostream& os, set<T>& set_var) {
    os << "{";
    repi(itr, set_var) {
        os << *itr;
        itr++;
        if (itr != set_var.end()) os << ", ";
        itr--;
    }
    os << "}";
    return os;
}
 
#define DUMPOUT cerr
 
void dump_func() {
    DUMPOUT << endl;
}
template <class Head, class... Tail>
void dump_func(Head&& head, Tail&& ... tail) {
    DUMPOUT << head;
    if (sizeof...(Tail) > 0) {
        DUMPOUT << ", ";
    }
    dump_func(std::move(tail)...);
}
#ifdef DEBUG
#define DEB
#define dump(...)                                                              \
    DUMPOUT << "  " << string(#__VA_ARGS__) << ": "                            \
            << "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]"        \
            << endl                                                            \
            << "    ",                                                         \
        dump_func(__VA_ARGS__)
#else
#define DEB if (false)
#define dump(...)
#endif

// http://beet-aizu.hatenablog.com/entry/2018/04/08/145516
template<typename T>
vector<T> make_v(size_t a){return vector<T>(a);}

template<typename T,typename... Ts>
auto make_v(size_t a,Ts... ts){
  return vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));
}

template<typename T,typename V>
typename enable_if<is_class<T>::value==0>::type
fill_v(T &t,const V &v){t=v;}

template<typename T,typename V>
typename enable_if<is_class<T>::value!=0>::type
fill_v(T &t,const V &v){
  for(auto &e:t) fill_v(e,v);
}

#endif


#define mod 1000000007
typedef pair<int, int> P;
#define INF (1LL<<60)

struct Edge {
    int to;     // 辺の行き先
    int weight; // 辺の重み
    Edge(int t, int w) : to(t), weight(w) { }
};
using Graph = vector<vector<Edge>>;

const int dx[2] = { 1, 0 };
const int dy[2] = { 0, 1 };

typedef pair<int, int> P;

vector<int> Dijkstra(Graph &G, int r){
    int V = G.size();
    vector<int> dist(V, INF);
    priority_queue<P, vector<P>, greater<P> > pq;
    dist[r] = 0;
    pq.push(P(0, r));

    while(!pq.empty()){
        P p = pq.top();
        pq.pop();
        int v = p.second;
        if(dist[v]<p.first) continue;
        for(int i=0;i<G[v].size();i++){
            Edge e = G[v][i];
            if(dist[e.to] <= dist[v] + e.weight) continue;
            dist[e.to] = dist[v] + e.weight;
            pq.push(P(dist[e.to], e.to));
        }
    }
    return dist;
}

void solve(){
    
    int H, W;
    cin >> H >> W;
    
    auto Z = [&](int a, int b){ return a*W + b;};
    
    auto A = make_v<char>(H,W);
    rep(i,H)rep(j,W) cin >> A[i][j];
    
    Graph G;

    G.resize(Z(H-1,W-1)+1);
    rep(i,H)rep(j,W){
        rep(k,2){
            int ni = i+dx[k];
            int nj = j+dy[k];

            if(0<=ni && ni<H && 0<=nj && nj<W){
                int cost;
                if(A[i][j]!=A[ni][nj]) cost=1;
                else cost=0;
                G[Z(i,j)].push_back({Z(ni,nj),cost});
            }
        }
    }
    
    auto dist = Dijkstra(G, Z(0,0));
    
    dump(dist);
    
    int ans = dist[Z(H-1,W-1)];
    if(A[0][0]=='.' && A[H-1][W-1]=='.') ans/=2;
    else if(A[0][0]=='#' && A[H-1][W-1]=='#')
        ans = ans/2+1;
    else
        ans = (ans+1)/2;
    
    
    cout << ans << endl;
    
    

}

signed main(){
    cout << fixed << setprecision(18);
    cerr << fixed << setprecision(18);
    solve();
}


Measured memory_bytes: 1024