#include <bits/stdc++.h>  // clang-format off
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define each(x,v) for(auto& x : v)
#define all(v) (v).begin(),(v).end()
#define sz(v) ((int)(v).size())
#define ini(...) int __VA_ARGS__; in(__VA_ARGS__)
#define inl(...) long long __VA_ARGS__; in(__VA_ARGS__)
#define ins(...) string __VA_ARGS__; in(__VA_ARGS__)
#define inc(...) char __VA_ARGS__; in(__VA_ARGS__)
#define in2(s,t)     rep(i,sz(s)){in(s[i] , t[i]);}
#define in3(s,t,u)   rep(i,sz(s)){in(s[i] , t[i] , u[i]);}
#define in4(s,t,u,v) rep(i,sz(s)){in(s[i] , t[i] , u[i] , v[i]);}
#ifdef ONLINE_JUDGE
  #define rep(i,N) for(int i = 0; i < (int)(N); i++)
  #define repr(i,N) for(int i = (int)(N) - 1; i >= 0; i--)
  #define rep1(i,N) for(int i = 1; i <= (int)(N) ; i++)
  #define repr1(i,N) for(int i = (N) ; (int)(i) > 0 ; i--)
#else
  #define rep(i,N) for(long long i = 0; i < (long long)(N); i++)
  #define repr(i,N) for(long long i = (long long)(N) - 1; i >= 0; i--)
  #define rep1(i,N) for(long long i = 1; i <= (long long)(N) ; i++)
  #define repr1(i,N) for(long long i = (N) ; (long long)(i) > 0 ; i--)
#endif
using namespace std; void solve();
using ll = long long; template<class T = ll> using V = vector<T>;
using vi = V<int>; using vl = V<>; using vvi = V< V<int> >;
using vd = V<double>; using vs = V<string>; using vvl = V< V<> >;
constexpr int inf = 1001001001; constexpr ll infLL = (1LL << 61) - 1;
template<typename T, typename U> inline bool amin(T &x, U y) { return (y < x) ? (x = y, true) : false; }
template<typename T, typename U> inline bool amax(T &x, U y) { return (x < y) ? (x = y, true) : false; }
template<typename T,typename U>ll ceil(T a,U b){return (a + b - 1) / b;}
template<typename T, typename U> ostream& operator <<(ostream& os, const pair<T, U> &p) { os << p.first << " " << p.second; return os; }
template<typename T, typename U> istream& operator >>(istream& is, pair<T, U> &p) { is >> p.first >> p.second; return is; }
template<typename T> ostream& operator <<(ostream& os, const vector<T> &v) { int s = (int)v.size(); for(int i=0;i<s;i++) os << (i ? " " : "") << v[i]; return os; }
template<typename T> istream& operator >>(istream& is, vector<T> &v) { for(auto &x : v) is >> x; return is; }
void in(){} template <typename T,class... U> void in(T &t,U &...u){ cin >> t; in(u...);}
void out(){cout << "\n";} template <typename T,class... U> void out(const T &t,const U &...u){ cout << t; if(sizeof...(u)) cout << " "; out(u...);}
template<typename T>void die(T x){out(x); exit(0);}

#ifdef NyaanDebug
  #include "NyaanDebug.h"
  #define trc(...) do { cerr << #__VA_ARGS__ << " = "; dbg_out(__VA_ARGS__);} while(0)
  #define trca(v,N) do { cerr << #v << " = "; array_out(v , N);} while(0)
  #define trcc(v) do { cerr << "name : " << #v << "\n"; int cnt = 0; each(x , v){cerr << (cnt++) << " : "; trc(x); } } while(0)
#else
  #define trc(...)
  #define trca(...)
  #define trcc(...)
  int main(){solve();}
#endif

constexpr ll TEN(int n){ll ret=1,x=10;while(n){if(n&1)ret*=x;x*=x;n>>=1;}return ret;}
#define mem(a, val) memset(a, val, sizeof(a))

struct IoSetupNya {IoSetupNya() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); cerr << fixed << setprecision(7);} } iosetupnya;
using P = pair<ll,ll>; using vp = V<P>;
constexpr int MOD = /** 1000000007; //*/ 998244353;
// clang-format on
////////////////////////////////////////////////////


template<typename T>
struct BIT2D{
  int H,W;
  vector<vector<T>> bit;
  BIT2D(int H,int W):H(H),W(W){
    bit.resize(H + 1 , vector<T>(W + 1 , 0));
  }
  // 関数の入力のindexは0-originを想定

  // (x,y)にwを足す
  // 範囲外の時は足さない
  void add(int x, int y, T w){
    if(x < 0 || x >= H || y < 0 || y >= W) return;
    for(int a = (++y , ++x); a <= H; a += a & -a){
      for(int b = y ; b <= W; b += b & -b){
        bit[a][b] += w;
      }
    }
  }

  // imos法で[(x1,y1) , (x2,y2)]にwを足す
  void imos(int x1, int y1, int x2, int y2, T w){
    add(x1 , y1 , w);
    add(x1 , y2 + 1 , -w);
    add(x2 + 1 , y1 , -w);
    add(x2 + 1 , y2 + 1 , w);
  }

  //  [(0,0) , (x,y)]の和　閉区間に注意！
  // x,y<0の時は0 x>=H y>=Wのときはx=H-1,y=W-1とみなす
  // ( imos法の時は (x,y)の値を返す )
  T sum(int x, int y){
    if(x < 0 || y < 0) return 0;
    if(x >= H) x = H - 1;
    if(y >= W) y = W - 1;
    T ret = 0;
    for(int a = (++y , ++x) ; a > 0; a -= a & -a){
      for(int b = y; b > 0; b -= b & -b){
        ret += bit[a][b];
      }
    }
    return ret;
  }

  // [(x1,y1) , (x2,y2)] の和
  // x1 > x2, y1 > y2の時はswap
  T sum(int x1,int y1, int x2, int y2){
    if(x1 > x2 || y1 > y2) return T(0);
    return sum(x2,y2)-sum(x2,y1-1)-sum(x1-1,y2)+sum(x1-1,y1-1);
  }
};

int dp[110][110][2];

void solve() {
  ini(H, W);
  vs g(H); in(g);

  // 0 白マス 1 黒マス
  dp[0][0][0] = (g[0][0] == '.' ? 0 : inf);
  dp[0][0][1] = (g[0][0] == '#' ? 1 : inf);
  trc(dp[0][0][0],dp[0][0][1]);

  rep(i , H) rep(j , W){
    if(i == 0 && j == 0) continue;
    dp[i][j][0] = dp[i][j][1] = inf;
    if(g[i][j] == '.'){
      if(i != 0){
        amin(dp[i][j][0],min(dp[i-1][j][0],dp[i-1][j][1]));
      }
      if(j != 0){
        amin(dp[i][j][0],min(dp[i][j-1][0],dp[i][j-1][1]));
      }
    }
    else{
      if(i != 0){
        amin(dp[i][j][1],min(dp[i-1][j][0] + 1,dp[i-1][j][1]));
      }
      if(j != 0){
        amin(dp[i][j][1],min(dp[i][j-1][0] + 1,dp[i][j-1][1]));
      }
    }
    trc(i,j,dp[i][j][0],dp[i][j][1]);
  }
  out(min(dp[H-1][W-1][0] , dp[H-1][W-1][1]));

  
  


  
}

Measured memory_bytes: 384