#include <bits/stdc++.h>
#define file(name) if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
using namespace std;
const int N = 4005;
const int dx[] = {0, 0, -1, 1};
const int dy[] = {-1, 1, 0, 0};
int r, c;
string a[N];
bool vis[N][N];
int ans;
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 _ = 0; _ < 4; ++_) {
int nx = x + dx[_];
int ny = y + dy[_];
if(nx < 0 || nx >= r || ny < 0 || ny >= c || a[nx][ny] == '.' || vis[nx][ny]) continue;
vis[nx][ny] = true;
if (a[nx][ny] != a[x][y]) q2.push(make_pair(nx, ny));
else q1.push(make_pair(nx, ny));
}
}
bfs(q2, q1);
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0), cout.tie(0);
// file("A") else file("task");
cin >> r >> c;
for(int i = 0; i < r; ++i) {
cin >> a[i];
}
queue<pair<int, int>> q1, q2;
q1.push(make_pair(0, 0));
vis[0][0] = true;
bfs(q1, q2);
cout << ans << '\n';
return 0;
}
