#include <bits/stdc++.h>
#ifdef __LOCAL
    #define DBG(X) cout << #X << " = " << (X) << endl;
    #define SAY(X) cout << (X) << endl;
#else
    #define DBG(X)
    #define SAY(X)
#endif

#ifdef __LOCAL
    #include <filesystem>
    namespace fs = std::filesystem;
#endif

using namespace std;

using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

int dx[]={1, 0, -1, 0, 1,-1, 1,-1};
int dy[]={0, 1, 0, -1, 1, 1,-1,-1};
const int INT_INF = (int)(2e9);
const ll  LL_INF = (ll)(2e18);
static mt19937 _g(time(nullptr));
 
inline ll randint(ll a, ll b) { ll w = (_g() << 31LL) ^ _g(); return a + w % (b - a + 1); }
inline void fast_io() { ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); };
template<typename T, typename S> inline ostream& operator<<(ostream& os, const pair<T, S> p) { cout << "[" << p.first << ";" << p.second << "]"; return os; }
template<typename T, typename S> inline ostream& operator<<(ostream& os, const map<T, S> p) { for (auto el : p) cout << "[" << el.first << ";" << el.second << "]"; return os; }
template<typename T> inline ostream& operator<<(ostream& os, const vector<T>& v) { for (auto el : v) cout << el << " "; return os; }
template<typename T> inline vector<T> fetch_vec(int sz) { vector<T> ret(sz); for (auto& elem : ret) cin >> elem; return ret; }

int H,W;
vector<string> S;
void input(){
    fast_io();
    #ifdef __LOCAL
        fs::path p = __FILE__;
        fs::path input,output;
        input = output = p.parent_path();
        input += string("/input/") + string(p.stem()) + string(".txt");
        output += string("/output/") + string(p.stem()) + string(".txt");
        freopen(input.c_str(), "r", stdin);
        freopen(output.c_str(), "w", stdout);
    #endif
    cin >> H >> W;
    for (int i = 0; i < H; i++)
    {
        string s;
        cin >> s;
        S.push_back(s);
    }
    
}

bool flip=false;
bool chk(pii now, pii next){
    if(S[0][0]=='.' || flip){
        return (S[now.first][now.second]=='.' && S[next.first][next.second]=='#');
    }
    if(S[0][0]=='#' && !flip){
        return flip = (S[now.first][now.second]=='#' && S[next.first][next.second]=='.');
    }
}

bool isgoal(pii now){
    return (now.first==(H-1) && now.second == (W-1));
}

bool isIn(pii now){
    return (0<=now.first and now.first<H and 0<=now.second and now.second<W);
}

int dfs(pii s){
    priority_queue<pair<int,pii>, vector<pair<int,pii>>, greater<pair<int,pii>>> pq;
    if(S[0][0]=='.') pq.push({0,s});
    else pq.push({1,s});
    int dist;
    vector<vector<bool>> visited(H,vector<bool>(W,false));
    pii now,next;
    while(!pq.empty()){
        tie(dist,now) = pq.top();
        pq.pop();
        if(visited[now.first][now.second]) continue;
        visited[now.first][now.second] = true;
        if(isgoal(now)) return dist;
        for (int i = 0; i < 2; i++)
        {
            next = now;
            next.first += dx[i];
            next.second += dy[i];
            if(!isIn(next)) continue;
            if(visited[next.first][next.second]) continue;
            int next_dist = dist;
            if(chk(now,next)) next_dist++;
            if(isgoal(next)) return next_dist;
            pq.push({next_dist,next});
        }
    }
}

int solve(){
    cout << dfs({0,0}) << endl;
    return 0;
}   

int main()
{
    input();
    solve();
    return 0;
}


Measured memory_bytes: 256