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

typedef long long ll;
typedef vector<ll> vll;
typedef vector<vector<ll>> vvll;
typedef vector<vector<vector<ll>>> vvvll;
typedef vector<bool> vb;
typedef vector<vector<bool>> vvb;
typedef vector<vector<vector<bool>>> vvvb;
typedef pair<ll, ll> pll;
typedef vector<pll> vpll;
typedef vector<vpll> vvpll;
typedef vector<double> vd;
typedef vector<vd> vdd;

#define FOR(i,x,y) for(ll i=(ll)x; i<(ll)y; ++i)
#define REP(i,y) FOR(i, 0, y)
#define RFOR(i,x,y) for(ll i=(ll)x; i>=(ll)y; --i)
#define RREP(i,x) RFOR(i, x, 0)
#define ALL(a) a.begin(), a.end()
#define pb push_back
#define debug_print(x...) cerr << "line " << __LINE__ << " : "; debug_print_in(x);

template <typename First>
void debug_print_in(First first){
  cerr << first << endl;
  return;
}

template <typename First, typename... Rest>
void debug_print_in(First first, Rest... rest){
  cerr << first << " ";
  debug_print_in(rest...);
  return;
}

void IN(void){
  return;
}

template <typename First, typename... Rest>
void IN(First& first, Rest&... rest){
  cin >> first;
  IN(rest...);
  return;
}

template <typename First>
void OUT(First first){
  cout << first << endl;
  return;
}

template <typename First, typename... Rest>
void OUT(First first, Rest... rest){
  cout << first << " ";
  OUT(rest...);
  return;
}

template<class t, class u> void chmax(t&a,u b){if(a<b)a=b;};
template<class t, class u> void chmin(t&a,u b){if(a>b)a=b;};
int popcount(int t){return __builtin_popcount(t);} //GCC
int popcount(ll t){return __builtin_popcountll(t);} //GCC

template <typename T>
void vec_print(vector<T> VEC){
  REP(i, VEC.size()){
    cerr << VEC[i] << " ";
  }
  cerr << endl;
};

template <typename T>
void mat_print(vector<vector<T> > MAT){
  REP(i,MAT.size()){
    REP(j,MAT[i].size()){
      cerr << MAT[i][j] << " ";
    }
    cerr << endl;
  }
};

constexpr int INF = (1<<30);
constexpr ll INFLL = 1LL<<62;
constexpr long double EPS = 1e-12;
constexpr ll MOD = (ll)((1E+9)+7);

ll H, W;
vvll S;
vvll C;

void search(void){
  queue<pair<ll, ll>> que;
  que.push(make_pair(0, 0));
  while(que.size()){
    pair<ll, ll> pos = que.front(); que.pop();
    ll h = pos.first;
    ll w = pos.second;
    if(h>=H) continue;
    if(w>=W) continue;
    ll tmp = INFLL;
    if(S[h][w]==0){
      if(h>0) chmin(tmp, C[h-1][w]);
      if(w>0) chmin(tmp, C[h][w-1]);
      if(h==0 && w==0) tmp=0;
    }else{
      if(h>0){
        if(S[h-1][w]==1) chmin(tmp, C[h-1][w]);
        else             chmin(tmp, C[h-1][w]+1);
      }
      if(w>0){
        if(S[h][w-1]==1) chmin(tmp, C[h][w-1]);
        else             chmin(tmp, C[h][w-1]+1);
      }
      if(h==0 && w==0) tmp=1;
    }
    if(C[h][w]<=tmp) continue;
    C[h][w] = tmp;
    que.push(make_pair(h+1, w));
    que.push(make_pair(h, w+1));
  }
  return;
}

int main(){
  cin.tie(0); // cut the cin and cout (default, std::flush is performed after std::cin)
  ios::sync_with_stdio(false); // cut the iostream and stdio (DON'T endl; BUT "\n";)

  IN(H,W);
  S.resize(H, vll(W, 0));
  REP(i,H){
    string str;
    IN(str);
    REP(j,W){
      if(str[j]=='#') S[i][j]=1;
    }
  }

  C.resize(H, vll(W, INFLL));

  search();

  //mat_print(C);

  OUT(C[H-1][W-1]);

  return 0;
}


Measured memory_bytes: 384