#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define SPEED ios_base::sync_with_stdio(false); cin.tie(NULL);
#define FOR(i, a, b) for (ll i = a; i < b; ++i)
#define RFOR(i, b, a) for (ll i = b; i >= a; --i)
#define ALL(x) x.begin(), x.end()
#define DEBUG(args...) { string _s = #args; replace(ALL(_s), ' ', '\0');\
replace(ALL(_s), ',', ' ');\
stringstream _ss(_s); istream_iterator<string> _it(_ss); _debug(_it, args);}
#define endl "\n"
#define F first
#define S second
#define pb(x) push_back(x)
#define mp(x, y) make_pair(x, y)

using namespace std;
using namespace __gnu_pbds;

template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

void _debug(istream_iterator<string>) {}
template<typename T, typename... Args>
void _debug(istream_iterator<string> it, T first, Args... args) {
    cerr << ">> " << *it << " : " << first << endl; _debug(++it, args...);
}
template <typename T1, typename T2>
inline ostream& operator << (ostream& out, const pair<T1, T2>& p) {
    return out << "(" << p.F << ", " << p.S << ")";
}
template<typename T>
inline ostream& operator << (ostream& out, const vector<T>& v) {
    if (v.empty()) return out << "[]";
    else { out << '['; for (auto& e : v) { out << e << ", "; } return out << "\b\b]"; }
}
template<typename T>
inline ostream& operator << (ostream& out, const set<T>& s) {
    if (s.empty()) return out << "{}";
    else { out << '{'; for (auto& e : s) { out << e << ", "; } return out << "\b\b}"; }
}
template<typename T>
inline ostream& operator << (ostream& out, const unordered_set<T>& s) {
    return out << set<T>(ALL(s));
}
template<typename T1, typename T2>
inline ostream& operator << (ostream& out, const map<T1, T2>& m) {
    if (m.empty()) return out << "{}";
    out << '{'; for (auto& p : m) { out << p << ", "; } return out << "\b\b}";
}
template<typename T1, typename T2>
inline ostream& operator << (ostream& out, const unordered_map<T1, T2>& m) {
    return out << map<T1, T2>(ALL(m));
}
template<typename T>
inline ostream& operator << (ostream& out, const ordered_set<T>& s) {
    return out << set<T>(ALL(s));
}

typedef long long ll;
typedef long double ld;
typedef vector<long long> vll;
typedef pair<ll, ll> pll;
typedef vector<pair<ll, ll>> vpll;
typedef unordered_map<ll, ll> STll;
/************************************** MAIN PROGRAM ********************************************/
const int MAX = 101;
bool dp[MAX][MAX][MAX][MAX][2];
int ans[MAX][MAX];
string grid[MAX];

int f(char ch) {
    return ch == '.' ? 0 : 1;
}

const int INF = 1e9;

int cost(int r, int c, int x, int y) {
    if (dp[r][c][x][y][0]) return 0;
    if (dp[r][c][x][y][1]) return 1;
    return INF;
}

int main()
{
   // freopen("input.txt", "r", stdin);
    SPEED
    int n, m;
    cin >> n >> m;
    for (int i = 0; i < n; ++i) {
        cin >> grid[i];
    }
    FOR(i, 0, MAX) {
        FOR(j, 0, MAX) {
            ans[i][j] = INF;
        }
    }
    for (int col : {0, 1}) {
        for (int i = 0; i < n; ++i) {
            for (int j = 0; j < m; ++j) {
                dp[i][j][i][j][col] = f(grid[i][j]) == col;
                for (int k = i; k < n; ++k) {
                    for (int l = j; l < m; ++l) {
                        if (k + 1 < n) {
                            dp[i][j][k + 1][l][col] |= dp[i][j][k][l][col] && f(grid[k + 1][l]) == col;
                        }
                        if (l + 1 <m) {
                            dp[i][j][k][l + 1][col] |= dp[i][j][k][l][col] && f(grid[k][l + 1]) == col;
                        }
                    }
                }
            }
        }
    }
   // DEBUG(dp[0][1][2][1][0])
    ans[0][0] = 0;
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < m; ++j) {
            for (int k = i; k < n; ++k) {
                for (int l = j; l < m; ++l) {
                    int cst = cost(i, j, k, l);
                    if (cst == INF) continue;
                    ans[k + 1][l] = min(ans[k + 1][l], cst + ans[i][j]);
                    ans[k][l + 1] = min(ans[k][l + 1], cst + ans[i][j]);
                }
            }
        }
    }
    cout << min(ans[n - 1][m], ans[n][m - 1]);
}
/************************************** END OF PROGRAM ******************************************/
/** Stuff you should look for:
 * int overflow, array bounds, over-counting
 * special cases (n=1?), set/unordered_set TLE, multi-set/set error
 * do something instead of nothing and stay organized
 */


Measured memory_bytes: 203008