#include <bits/stdc++.h>
using namespace std;
const int N = 4005;
int n, m, ans = 0;
bool visited[N][N];
char a[N][N];
int dx[4] = {0, -1, 0, 1};
int dy[4] = {-1, 0, 1, 0};
bool ok (int x, int y) {
return (x >= 1 && x <= n && y >= 1 && y <= m && !visited[x][y] && a[x][y] != '.');
}
void bfs (queue <pair <int, int> > q1, queue <pair <int, int> > q2) {
if (q1.empty()) return;
ans++;
while (!q1.empty()) {
int x = q1.front().first, y = q1.front().second; q1.pop();
for (int i = 0; i < 4; i++) {
int nx = x + dx[i];
int ny = y + dy[i];
if (!ok(nx, ny)) continue;
visited[nx][ny] = true;
if (a[nx][ny] == a[x][y]) q1.push({nx, ny});
else q2.push({nx, ny});
}
}
bfs(q2, q1);
}
int main(){
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin >> n >> m;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
cin >> a[i][j];
}
}
queue <pair <int, int> > q1, q2;
q1.push({1, 1});
visited[1][1] = true;
bfs(q1, q2);
cout << ans;
return 0;
}
