#include <bits/stdc++.h>
using namespace std;
#define fast ios::sync_with_stdio(0);cin.tie(0);
typedef long long ll;
#define f first
#define s second
#define MOD 1000000007
#define LOGN 20
#define MAXN 1000005
const int delRow[] = {-1, 0, 0, 1};
const int delCol[] = {0, -1, 1, 0};
int H, W;
vector<string> grid;
queue<pair<int,int>> q, new_q;
int main() {
fast
cin >> H >> W;
grid = vector<string>(H);
for (int i = 0; i < H; i++)
cin >> grid[i];
vector<vector<int>> vis(H, vector<int>(W, false));
q.push({0,0});
int cnt = 1;
while (!q.empty()) {
pair<int,int> temp = q.front();
q.pop();
int row = temp.f;
int col = temp.s;
vis[row][col] = true;
for (int i = 0; i < 4; i++) {
int nRow = delRow[i] + row;
int nCol = delCol[i] + col;
if (nRow >= 0 && nCol >= 0 && nRow < H && nCol < W && !vis[nRow][nCol] && grid[nRow][nCol] != '.') {
if (grid[nRow][nCol] == grid[row][col])
q.push({nRow, nCol});
else
new_q.push({nRow, nCol});
}
}
if (q.empty() && !new_q.empty()) {
q = new_q;
cnt++;
new_q = queue<pair<int,int>>();
}
}
cout << cnt << "\n";
}
