// Zende bad Shoma nasime faghat !
#include <bits/stdc++.h>
#define pb push_back
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define debug(x) cerr << #x << " : " << x << '\n'
using namespace std;
typedef long long ll;
typedef long double ld;
typedef string str;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
const ll Mod = 1000000007LL;
const int N = 4e3 + 10;
const ll Inf = 2242545357980376863LL;
const ll Log = 30;
int n, m, dis[N][N];
str A[N];
pii adj[] = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
deque<pii> dq;
inline bool val(int x, int y){
return (0 <= x) && (x < n) && (0 <= y) && (y < m) && (A[x][y] != '.');
}
int main(){
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n >> m;
for(int i = 0; i < n; i++)
cin >> A[i];
if(A[0][0] == '.') return cout << "0\n", 0;
memset(dis, 31, sizeof dis);
dis[0][0] = 1;
dq.pb({0, 0});
int x, y, nx, ny;
int ans = 1;
while(!dq.empty()){
x = dq.front().F; y = dq.front().S;
dq.pop_front();
//cerr << "# " << x << ' ' << y << '\n';
for(auto &[X, Y] : adj){
nx = x + X; ny = y + Y;
//cerr << nx << ' ' << ny << '\n';
//if(val(nx, ny)) cerr << nx << ' ' << ny << ' ' << A[nx][ny] << '\n';
if(val(nx, ny) && dis[nx][ny] > dis[x][y] + (A[x][y] == A[nx][ny] ? 0 : 1)){
if(A[x][y] == A[nx][ny]){
dis[nx][ny] = dis[x][y];
dq.push_front({nx, ny});
} else {
dis[nx][ny] = dis[x][y] + 1;
dq.push_back({nx, ny});
ans = dis[nx][ny];
}
}
}
}
cout << ans << '\n';
return 0;
}
