#include <bits/stdc++.h>
using namespace std;
template <typename T1, typename T2> istream &operator>>(istream &is, pair<T1, T2> &pa) { is >> pa.first >> pa.second; return is; }
template <typename T> istream &operator>>(istream &is, vector<T> &vec) { for (auto &v : vec) is >> v; return is; }
template <typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &pa) { os << "(" << pa.first << "," << pa.second << ")"; return os; }
template <typename T> ostream &operator<<(ostream &os, const vector<T> &vec) { os << "["; for (auto v : vec) os << v << ","; os << "]"; return os; }
template <typename T> ostream &operator<<(ostream &os, const deque<T> &vec) { os << "deq["; for (auto v : vec) os << v << ","; os << "]"; return os; }
template <typename T> ostream &operator<<(ostream &os, const set<T> &vec) { os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template <typename T> ostream &operator<<(ostream &os, const multiset<T> &vec) { os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template <typename T> ostream &operator<<(ostream &os, const unordered_set<T> &vec) { os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template <typename T> ostream &operator<<(ostream &os, const unordered_multiset<T> &vec) { os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template <typename TK, typename TV> ostream &operator<<(ostream &os, const unordered_map<TK, TV> &mp) { os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; }
template <typename TK, typename TV> ostream &operator<<(ostream &os, const map<TK, TV> &mp) { os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; }
template <typename T> void resize_array(vector<T> &vec, int len) { vec.resize(len); }
template <typename T, typename... Args> void resize_array(vector<T> &vec, int len, Args... args) { vec.resize(len); for (auto &v : vec) resize_array(v, args...); }
template <typename T1, typename T2> pair<T1, T2> operator+(const pair<T1, T2> &l, const pair<T1, T2> &r) { return make_pair(l.first + r.first, l.second + r.second); }
template <typename T1, typename T2> pair<T1, T2> operator-(const pair<T1, T2> &l, const pair<T1, T2> &r) { return make_pair(l.first - r.first, l.second - r.second); }
long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
mt19937 mrand(random_device{}());
int rnd(int x) { return mrand() % x; }
template <unsigned int MOD>
class ModInt {
public:
// static unsigned int MOD;
ModInt(unsigned long long _v = 0) { set_v((_v % MOD + MOD)); }
explicit operator bool() const { return val != 0; }
ModInt operator-() const { return ModInt() - *this; }
ModInt operator+(const ModInt &r) const { return ModInt().set_v(val + r.val); }
ModInt operator-(const ModInt &r) const { return ModInt().set_v(val + MOD - r.val); }
ModInt operator*(const ModInt &r) const { return ModInt().set_v((unsigned int)((unsigned long long)(val)*r.val % MOD)); }
ModInt operator/(const ModInt &r) const { return *this * r.inv(); }
ModInt &operator+=(const ModInt &r) { return *this = *this + r; }
ModInt &operator-=(const ModInt &r) { return *this = *this - r; }
ModInt &operator*=(const ModInt &r) { return *this = *this * r; }
ModInt &operator/=(const ModInt &r) { return *this = *this / r; }
// ModInt &operator=(unsigned long long _v) { set_v((_v % MOD + MOD)); return *this; }
unsigned int operator=(unsigned long long _v) { set_v((_v % MOD + MOD)); return val; }
bool operator==(const ModInt &r) const { return val == r.val; }
bool operator!=(const ModInt &r) const { return val != r.val; }
ModInt pow(long long n) const {
ModInt x = *this, r = 1;
while (n) {
if (n & 1)
r *= x;
x *= x;
n >>= 1;
}
return r;
}
ModInt inv() const { return pow(MOD - 2); }
unsigned int get_val() { return val; }
friend ostream &operator<<(ostream &os, const ModInt &r) { return os << r.val; }
friend istream &operator>>(istream &is, ModInt &r) { return is >> r.val; }
private:
unsigned int val;
ModInt &set_v(unsigned int _v) {
val = (_v < MOD) ? _v : _v - MOD;
return *this;
}
};
// constexpr unsigned int mod = 1e9+7;
constexpr unsigned int mod = 998244353;
using Mint = ModInt<mod>;
#define rep(i, a, n) for (int i = a; i < (n); i++)
#define per(i, a, n) for (int i = (n)-1; i >= a; i--)
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(), (x).end()
#define fi first
#define se second
#define sz(x) ((int)(x).size())
typedef vector<int> vi;
typedef long long ll;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef double db;
#if DEBUG
#define dbg(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ") " << __FILE__ << endl;
#else
#define dbg(x)
#endif
using Mint2 = ModInt<mod-1>;
// unsigned int ModInt::MOD = 0;
class Solution {
public:
void Solve() {
int dir[4][2] = {{-1,0},{1,0},{0,-1},{0,1}};
int h,w;
while (cin>>h>>w) {
vector<string> grid(h);
rep(i,0,h) cin>>grid[i];
vector<vi> dis(h, vi(w, numeric_limits<int>::max()));
deque<pii> q;
q.emplace_back(mp(0,0));
dis[0][0] = 0;
int ans = 0;
while(!q.empty()) {
auto u = q.front(); q.pop_front();
ans = dis[u.first][u.second] + 1;
rep(i,0,4) {
pii v = mp(u.first+dir[i][0], u.second+dir[i][1]);
if (v.first <0 || v.first >= h || v.second <0 || v.second >=w) continue;
if (grid[v.first][v.second] == '.') continue;
// dbg(v);
int d = grid[u.first][u.second] != grid[v.first][v.second];
if (dis[v.first][v.second] > dis[u.first][u.second] + d) {
dis[v.first][v.second] = dis[u.first][u.second] + d;
if (d==1) q.emplace_back(v);
else q.emplace_front(v);
}
}
}
cout << ans << endl;
}
}
private:
};
// #define USACO 1
void set_io(const string &name = "") {
ios::sync_with_stdio(false);
cin.tie(nullptr);
#if FILE_IO || USACO
if (!name.empty()) {
freopen((name + ".in").c_str(), "r", stdin);
freopen((name + ".out").c_str(), "w", stdout);
}
#endif
}
int main() {
#if USACO
set_io("odometer");
#else
set_io("input");
#endif
Solution().Solve();
return 0;
}
