#include <bits/stdc++.h>

using namespace std;

#define forn(a, e) for (int a = 0; a < (int)(e); a++)
#define forr(a, s, e) for (int a = s; a < (int)(e); a++)
#define fore(e, a) for (auto& e : a)

#ifdef LOCAL
#define logv(a) {cerr << #a << " = "; fore(e, a) {cerr << e << " ";} cerr << "\n";}
#define logvp(a) {cerr << #a << " = "; fore(e, a) {cerr << "(" << e.first << ", " << e.second << ") ";} cerr << "\n";}
#define logvv(a) {cerr << #a << " = \n"; fore(r, a) { fore(e, r) {cerr << e << " ";} cerr << "\n";} }
#define logvf(a, field) {cerr << #a"."#field << " = \n"; fore(e, a) { cerr << e.field << " ";} cerr << "\n"; }
#define logvff(a, f1, f2) {cerr << #a".{"#f1 << ", "#f2 << "} = \n"; fore(e, a) { cerr << "(" << e.f1 <<", " << e.f2 << ") ";} cerr << "\n"; }
#define logs(a) cerr << #a << " = " << (a) << "\n";
#define logss(a, b) cerr << #a << " = " << (a) << ", " << #b << " = " << (b) << "\n";
#define logp(a) cerr << #a << " = " << "(" << a.first << ", " << a.second << ")" << "\n";
#define cond(pred, stmt) if (pred) { stmt }
#else
#define logv(a)
#define logvp(a)
#define logvv(a)
#define logvf(a, field)
#define logvff(a, f1, f2)
#define logs(a)
#define logss(a, b)
#define logp(a)
#define cond(pred, stmt)
#endif

using i64 = long long;
using iip = pair<i64, i64>;
using ivec = vector<int>;
using llvec = vector<i64>;
using svec = vector<string>;
template<typename T> using vec = vector<T>;

template<typename T, typename Dim>
auto make_vec(T value, Dim dim) { return vector<T>(dim, value); }
template<typename T, typename Dim1, typename... Dim>
auto make_vec(T value, Dim1 dim1, Dim... dims) { return make_vec(make_vec(value, dims...), dim1); }

template<typename T>
bool uax(T& v, const T& newv) { if (v < newv) { v = newv; return true; } else return false; }
template<typename T>
bool uin(T& v, const T& newv) { if (v > newv) { v = newv; return true; } else return false; }

template<typename T>
istream& operator>>(istream& is, vector<T>& c) { for (auto& e : c) is >> e; return is; }

template<typename ...T>
istream& read(T&... args) { return (cin >> ... >> args); }

static mt19937 rande(123123);
template<typename T>
T rand_int(T from, T to) { uniform_int_distribution<T> distr(from, to); return distr(rande); }

const i64 M = 1e9 + 7;
const int INF = 1e9 + 1;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    int n, m;
    while (read(n, m)) {
        svec a(n);
        read(a);

        auto dp = make_vec(INF, n, m);
        dp[n - 1][m - 1] = (a[n - 1][m - 1] == '#');
        for (int i = n - 1; i >= 0; i--) {
            for (int j = m - 1; j >= 0; j--) {
                auto rs = make_vec(0, n, m);
                rs[i][j] = true;
                forr(k, i, n) forr(p, j, m) {
                    if (k != i && a[k][p] == a[k - 1][p]) {
                        rs[k][p] |= rs[k - 1][p];                        
                        
                    }
                    if (k != i && rs[k - 1][p]) {
                        uin(dp[i][j], dp[k][p] + (a[i][j] == '#'));
                    }
                    if (p != j && a[k][p] == a[k][p - 1]) {
                        rs[k][p] |= rs[k][p - 1];                        
                    }
                    if (p != j && rs[k][p - 1]) {
                        uin(dp[i][j], dp[k][p] + (a[i][j] == '#'));
                    }

                    if (rs[k][p]) {
                        uin(dp[i][j], dp[k][p]);
                    }
                }
            }
        }
        logvv(dp);
        cout << dp[0][0] << endl;
    }
}


Measured memory_bytes: 3648