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

using ll = long long;
using Vi = std::vector<int>;
using Vl = std::vector<ll>;
using Pii = std::pair<int, int>;
using Pll = std::pair<ll, ll>;

constexpr int I_INF = std::numeric_limits<int>::max();
constexpr ll L_INF = std::numeric_limits<ll>::max();

template <typename T1, typename T2>
inline bool chmin(T1& a, const T2& b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <typename T1, typename T2>
inline bool chmax(T1& a, const T2& b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

template <std::ostream& os = std::cout>
class Prints {
private:
    class __Prints {
    public:
        __Prints(const char* sep, const char* term) : sep(sep), term(term) {}
        template <class... Args>
        auto operator()(const Args&... args) const -> decltype((os << ... << std::declval<Args>()), void()) { print(args...); }
        template <typename T>
        auto pvec(const T& vec, size_t sz) const -> decltype(os << std::declval<decltype(std::declval<T>()[0])>(), void()) {
            for (size_t i = 0; i < sz; i++)
                os << vec[i] << (i == sz - 1 ? term : sep);
        }
        template <typename T>
        auto pmat(const T& mat, size_t h, size_t w) -> decltype(os << std::declval<decltype(std::declval<T>()[0][0])>(), void()) {
            for (size_t i = 0; i < h; i++)
                for (size_t j = 0; j < w; j++)
                    os << mat[i][j] << (j == w - 1 ? term : sep);
        }

    private:
        const char *sep, *term;
        void print() const { os << term; }
        void print_rest() const { os << term; }
        template <class T, class... Tail>
        void print(const T& head, const Tail&... tail) const { os << head, print_rest(tail...); }
        template <class T, class... Tail>
        void print_rest(const T& head, const Tail&... tail) const { os << sep << head, print_rest(tail...); }
    };

public:
    Prints() {}
    __Prints operator()(const char* sep = " ", const char* term = "\n") const { return __Prints(sep, term); }
};

Prints<> prints;
Prints<std::cerr> prints_err;

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

void solve() {
    int H, W;
    cin >> H >> W;
    vector<string> grid(H);
    for (ll i = 0; i < H; i++) {
        cin >> grid[i];
    }
    int ans = 0;
    for (ll i = 0; i < H - 1; i++) {
        for (ll j = 0; j < W - 1; j++) {
            int cntW = 0;
            if (grid[i][j] == '.') ++cntW;
            if (grid[i + 1][j] == '.') ++cntW;
            if (grid[i][j + 1] == '.') ++cntW;
            if (grid[i + 1][j + 1] == '.') ++cntW;
            if (cntW == 1 || cntW == 3) ++ans;
        }
    }
    prints()(ans);
}

//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

int main() {
#ifdef FASTIO
    std::cin.tie(nullptr), std::cout.tie(nullptr);
    std::ios::sync_with_stdio(false);
#endif
#ifdef FILEINPUT
    std::ifstream ifs("./in_out/input.txt");
    std::cin.rdbuf(ifs.rdbuf());
#endif
#ifdef FILEOUTPUT
    std::ofstream ofs("./in_out/output.txt");
    std::cout.rdbuf(ofs.rdbuf());
#endif
    std::cout << std::setprecision(18) << std::fixed;
    solve();
    std::cout << std::flush;
    return 0;
}
#include <bits/stdc++.h>
using namespace std;

int main(){
  int H, W;
  cin >> H >> W;
  vector<vector<char>> v(H,vector<char>(W));
  for(int i = 0;i < H;i++){
    for(int j = 0;j < W;j++)
      cin >> v.at(i).at(j);
  }
  int ans = 0;
  for(int i = 1;i< H;i++){
    for(int j = 1;j < W;j++){
        int ij = 0;
        if(v.at(i).at(j) == '#')
          ij = 1;
        int hu = 0;
        if(v.at(i - 1).at(j - 1) == '#')
          hu = 1;
        int un = 0;
        if(v.at(i - 1).at(j) == '#')
          un = 1;
        int hn = 0;
        if(v.at(i).at(j - 1) == '#')
          hn = 1;
        if((hu + hn + un + ij) % 2 == 1)
          ans += 1;
      }
    }
  cout << ans << endl;
}