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

#define int long long
#define double long double
#define rep(i, n) for (int i = 0; i < (n); i++)
#define reps(i, n) for (int i = 1; i <= (n); i++)
#define all(x) begin(x), end(x)
#define uniq(x) (x).erase(unique(all(x)), end(x))
#define bit(n) (1LL << (n))
#define dump(x) cerr << #x " = " << (x) << endl
using vint = vector<int>;
using vvint = vector<vint>;
using pint = pair<int, int>;
using vpint = vector<pint>;
template<typename T> using priority_queue_rev = priority_queue<T, vector<T>, greater<T>>;
constexpr double pi = 3.1415926535897932384626433832795028L;
constexpr int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};
constexpr int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
int gcd(int a, int b) {
    while (b) { swap(a %= b, b); }
    return a;
}
int lcm(int a, int b) { return a / gcd(a, b) * b; }
template<typename T> void fin(T mes) {
    cout << mes << endl;
    exit(0);
}
template<typename T, typename U> bool chmax(T &a, const U &b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
template<typename T, typename U> bool chmin(T &a, const U &b) {
    if (b < a) {
        a = b;
        return true;
    }
    return false;
}
template<typename T, typename U> ostream &operator<<(ostream &os, const pair<T, U> &rhs) {
    os << "(" << rhs.first << ", " << rhs.second << ")";
    return os;
}
template<typename T> ostream &operator<<(ostream &os, const vector<T> &rhs) {
    os << "{";
    for (auto itr = rhs.begin(); itr != rhs.end(); itr++) {
        os << *itr << (next(itr) != rhs.end() ? ", " : "");
    }
    os << "}";
    return os;
}
struct setup {
    static constexpr int PREC = 20;
    setup() {
        cout << fixed << setprecision(PREC);
        cerr << fixed << setprecision(PREC);
    };
} setup;

template<typename T>
struct dijkstra {
    struct edge {
        int to;
        T cost;
    };
    int n;
    T zero, inf;
    std::vector<std::vector<edge>> graph;
    dijkstra(int n, T zero = T(), T inf = std::numeric_limits<T>::max()) : n(n), zero(zero), inf(inf), graph(n) {}
    void add_edge(int from, int to, T cost) { graph[from].push_back({to, cost}); }
    std::vector<T> get_dist(int s) {
        using P = std::pair<T, int>;
        std::priority_queue<P, std::vector<P>, std::greater<P>> pq;
        std::vector<T> ret(n, inf);
        ret[s] = zero;
        pq.push({zero, s});
        while (!pq.empty()) {
            P p = pq.top();
            pq.pop();
            int v = p.second;
            if (ret[v] < p.first) { continue; }
            for (int i = 0; i < graph[v].size(); i++) {
                edge e = graph[v][i];
                T next_dist = ret[v] + e.cost;
                if (ret[e.to] <= next_dist) { continue; }
                ret[e.to] = next_dist;
                pq.push({ret[e.to], e.to});
            }
        }
        return ret;
    }
};

int H, W;
string M[110];
signed main() {
    cin >> H >> W;
    rep(i, H) {
        cin >> M[i];
    }
    dijkstra<int> dij(H * W);
    rep(i, H) {
        rep(j, W) {
            if (i < H - 1) {
                if (M[i][j] == '.' && M[i + 1][j] == '#') { dij.add_edge(i * W + j, (i + 1) * W + j, 1); }
                else { dij.add_edge(i * W + j, (i + 1) * W + j, 0); }
            }
            if (j < W - 1) {
                if (M[i][j] == '.' && M[i][j + 1] == '#') { dij.add_edge(i * W + j, i * W + (j + 1), 1); }
                else { dij.add_edge(i * W + j, i * W + (j + 1), 0); }
            }
        }
    }
    int ans = dij.get_dist(0)[H * W - 1];
    if (M[0][0] == '#') { ans++; }
    cout << ans << endl;
}


Measured memory_bytes: 1024