#include <bits/stdc++.h>
using namespace std;
#define pii pair<int, int>
#define fr first
#define se second
const int MAXT = 4e3 + 10;
char mat[MAXT][MAXT];
bool vis[MAXT][MAXT];
int n, m;
int x[] = {-1, 0, 0, 1};
int y[] = {0, -1, 1, 0};
bool valid(int i, int j) {
return ((1 <= i) && (n >= i) && (j >= 1) && (j <= m));
}
vector<pii> border;
void dfs(int i, int j) {
vis[i][j] = 1;
for (int k = 0; k < 4; k++) {
int a = (i + x[k]), b = (j + y[k]);
if (!valid(a, b) || vis[a][b] || (mat[a][b] == '.')) continue;
if (mat[i][j] != mat[a][b]) border.push_back({a, b});
else dfs(a, b);
}
}
int32_t main() {
cin >> n >> m;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
cin >> mat[i][j];
}
}
border.push_back({1, 1});
int ans = 0;
while (!border.empty()) {
ans++;
vector<pii> nb = border;
border.clear();
for (auto u : nb) dfs(u.fr, u.se);
}
cout << ans << "\n";
}
