#include<bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef long double ld;
using graph = vector<vector<int>>;
using pii = pair<int,int>;

#define rep(i,n) for(ll i=0;i<(ll)(n);i++)
#define repd(i,n) for(ll i=n-1;i>=0;i--)
#define FOR(i,a,b) for(ll i=a;i<=(ll)(b);i++)
#define FORD(i,a,b) for(ll i=a;i>=(ll)(b);i--)
//xにはvectorなどのコンテナ
#define all(x) (x).begin(),(x).end()
#define size(x) ((ll)(x).size())
#define MAX(x) *max_element(ALL(x))
#define MIN(x) *min_element(ALL(x))

#define INF 1000000000000
#define M 10000007
#define MAXR 100000

#define pb push_back
#define mp make_pair
#define f first
#define s second
#define FIND(x,y) find(all(x),y)!=x.end()
template<class T> inline bool chmax(T &a,T b) { if (a<b) { a=b; return true; } return false; }
template<class T> inline bool chmin(T &a,T b) { if (b<a) { a=b; return true; } return false; }

struct uf {
    vector<int> par; // par[i]:iの親の番号　(例) par[3] = 2 : 3の親が2
    vector<int> rcount;

    uf(int N) : par(N) { //最初は全てが根であるとして初期化
        for(int i = 0; i < N; i++) par[i] = i;
    }

    int root(int x) { // データxが属する木の根を再帰で得る：root(x) = {xの木の根}
        if (par[x] == x) return x;
        return par[x] = root(par[x]);
    }

    void unite(int x, int y) { // xとyの木を併合
        int rx = root(x); //xの根をrx
        int ry = root(y); //yの根をry
        if (rx == ry) return; //xとyの根が同じ(=同じ木にある)時はそのまま
        par[rx] = ry; //xとyの根が同じでない(=同じ木にない)時：xの根rxをyの根ryにつける
    }

    bool same(int x, int y) { // 2つのデータx, yが属する木が同じならtrueを返す
        int rx = root(x);
        int ry = root(y);
        return rx == ry;
    }

};
template<int MOD> struct Fp {
    long long val;
    constexpr Fp(long long v = 0) noexcept : val(v % MOD) {
        if (val < 0) val += MOD;
    }
    constexpr int getmod() { return MOD; }
    constexpr Fp operator - () const noexcept {
        return val ? MOD - val : 0;
    }
    constexpr Fp operator + (const Fp& r) const noexcept { return Fp(*this) += r; }
    constexpr Fp operator - (const Fp& r) const noexcept { return Fp(*this) -= r; }
    constexpr Fp operator * (const Fp& r) const noexcept { return Fp(*this) *= r; }
    constexpr Fp operator / (const Fp& r) const noexcept { return Fp(*this) /= r; }
    constexpr Fp& operator += (const Fp& r) noexcept {
        val += r.val;
        if (val >= MOD) val -= MOD;
        return *this;
    }
    constexpr Fp& operator -= (const Fp& r) noexcept {
        val -= r.val;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr Fp& operator *= (const Fp& r) noexcept {
        val = val * r.val % MOD;
        return *this;
    }
    constexpr Fp& operator /= (const Fp& r) noexcept {
        long long a = r.val, b = MOD, u = 1, v = 0;
        while (b) {
            long long t = a / b;
            a -= t * b; swap(a, b);
            u -= t * v; swap(u, v);
        }
        val = val * u % MOD;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr bool operator == (const Fp& r) const noexcept {
        return this->val == r.val;
    }
    constexpr bool operator != (const Fp& r) const noexcept {
        return this->val != r.val;
    }
    friend constexpr ostream& operator << (ostream &os, const Fp<MOD>& x) noexcept {
        return os << x.val;
    }
    friend constexpr Fp<MOD> modpow(const Fp<MOD> &a, long long n) noexcept {
        if (n == 0) return 1;
        auto t = modpow(a, n / 2);
        t = t * t;
        if (n & 1) t = t * a;
        return t;
    }
};


const int MOD = 1000000007;
using mint = Fp<MOD>;

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

bool flag=false;

int H, W,ans=10000000;
vector<string> field;

int seen[510][510];
void dfs(int h, int w,int gh,int gw) {
    rep(dir,2) {
    	flag=false;
        int nh = h + dy[dir];
        int nw = w + dx[dir];

        if (nh < 0 || nh >= H || nw < 0 || nw >= W) continue;
        if(field[h][w]!='#'&&field[nh][nw]=='#')flag=chmin(seen[nh][nw],seen[h][w]+1);
        else flag=chmin(seen[nh][nw],seen[h][w]);
        if(nh==gh&&nw==gw) continue;
        if(!flag)continue;

        dfs(nh, nw, gh ,gw);
    }
}

int main() {
    cin >> H >> W;
    field.resize(H);
    rep(h,H) cin >> field[h];

    int sh=0, sw=0, gh=H-1, gw=W-1;
    rep(i,H)rep(j,W)seen[i][j]=1000;
    seen[0][0]=0;
    dfs(sh, sw, gh, gw);
    if(field[0][0]=='#')seen[gh][gw]++;
    cout<<seen[gh][gw]<<endl;
}


Measured memory_bytes: 512