#include <bits/stdc++.h>
#define ALL(v) std::begin(v), std::end(v)
#define ALLR(v) std::rbegin(v), std::rend(v)
using ll = std::int64_t;
using ull = std::uint64_t;
using pii = std::pair<int, int>;
using tii = std::tuple<int, int, int>;
using pll = std::pair<ll, ll>;
using tll = std::tuple<ll, ll, ll>;
template <typename T> using vec = std::vector<T>;
template <typename T> using vvec = vec<vec<T>>;
template <typename T> const T& var_min(const T &t) { return t; }
template <typename T> const T& var_max(const T &t) { return t; }
template <typename T, typename... Tail> const T& var_min(const T &t, const Tail&... tail) { return std::min(t, var_min(tail...)); }
template <typename T, typename... Tail> const T& var_max(const T &t, const Tail&... tail) { return std::max(t, var_max(tail...)); }
template <typename T, typename... Tail> void chmin(T &t, const Tail&... tail) { t = var_min(t, tail...); }
template <typename T, typename... Tail> void chmax(T &t, const Tail&... tail) { t = var_max(t, tail...); }
template <typename T> const T& clamp(const T &t, const T &low, const T &high) { return std::max(low, std::min(high, t)); }
template <typename T> void chclamp(T &t, const T &low, const T &high) { return t = clamp(t, low, high); }
template <typename T> T make_v(T init) { return init; }
template <typename T, typename... Tail> auto make_v(T init, std::size_t s, Tail... tail) { auto v = std::move(make_v(init, tail...)); return vec<decltype(v)>(s, v); }
template <typename T, std::size_t Head, std::size_t ...Tail> struct multi_dem_array { using type = std::array<typename multi_dem_array<T, Tail...>::type, Head>; };
template <typename T, std::size_t Head> struct multi_dem_array<T, Head> { using type = std::array<T, Head>; };
template <typename T, std::size_t ...Args> using mdarray = typename multi_dem_array<T, Args...>::type;
namespace init__ { struct InitIO { InitIO() { std::cin.tie(nullptr); std::ios_base::sync_with_stdio(false); std::cout << std::fixed << std::setprecision(30); } } init_io; }

namespace graph {

using Node = ll;
using Weight = ll;
using Edge = std::pair<Node, Weight>;

template <bool Directed>
struct Graph : public vvec<Edge> {
    using vvec<Edge>::vvec;

    void add_edge(Node f, Node t, Weight w = 1) {
        (*this)[f].emplace_back(t, w);
        if (!Directed) (*this)[t].emplace_back(f, w);
    }

    Graph<Directed> build_inv() const {
        Graph<Directed> ret(this->size());
        for (Node i = 0; i < this->size(); i++) {
            for (const Edge &e : (*this)[i]) {
                Node j;
                Weight w;
                std::tie(j, w) = e;
                if (!Directed && j < i) continue;
                ret.add_edge(j, i, w);
            }
        }

        return ret;
    }
};

}

const ll inf = 5e15;

ll solve() {
    ll H, W;
    std::cin >> H >> W;
    vec<ll> dist(H * W, inf);
    vec<std::string> vs(H);
    for (auto &&e : vs) std::cin >> e;
    ll ans = (vs[0][0] == '#');

    auto valid = [&](ll h, ll w) {
        return 0 <= h && h < H &&
               0 <= w && w < W;
    };

    auto make_id = [&](ll h, ll w) {
        return W * h + w;
    };

    graph::Graph<true> g(H * W);

    ll dh[] = { 1, 0, };
    ll dw[] = { 0, 1, };

    for (ll h = 0; h < H; h++) for (ll w = 0; w < W; w++) {
        ll id = make_id(h, w);
        for (ll i = 0; i < 2; i++) {
            ll nh = h + dh[i];
            ll nw = w + dw[i];
            if (!valid(nh, nw)) continue;
            ll nid = make_id(nh, nw);
            g.add_edge(id, nid, vs[h][w] == '.' &&  vs[nh][nw] == '#');
        }
    }

    dist[0] = 0;
    std::deque<pll> deq;
    deq.emplace_back(0, 0);
    while (deq.size()) {
        ll d, id;
        std::tie(d, id) = deq.front();
        deq.pop_front();
        if (dist[id] < d) continue;
        for (auto &&e : g[id]) {
            ll nxt, c;
            std::tie(nxt, c) = e;
            ll nd = d + c;
            if (dist[nxt] <= nd) continue;
            dist[nxt] = nd;
            if (d == nd) deq.emplace_front(nd, nxt);
            else deq.emplace_back(nd, nxt);
        }
    }

    ans += dist[make_id(H - 1, W - 1)];
    return ans;
}

int main() {
    std::cout << solve() << '\n';
    return 0;
}


Measured memory_bytes: 1024