#include <bits/stdc++.h>
using namespace std;
const int dx[] = {0, 0, 1, -1};
const int dy[] = {1, -1, 0, 0};
int main() {
// Optimize I/O operations
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int r, c;
if (!(cin >> r >> c)) return 0;
vector<string> g(r);
for (int i = 0; i < r; i++) {
cin >> g[i];
}
// dist array tracks the minimum "character changes" to reach each cell
vector<vector<int>> dist(r, vector<int>(c, -1));
deque<pair<int, int>> dq;
// Start at top-left
dq.push_back({0, 0});
dist[0][0] = 1; // 1 represents the first animal
int max_animals = 1;
while (!dq.empty()) {
auto [x, y] = dq.front();
dq.pop_front();
// Keep track of the maximum distance reached anywhere in the grid
max_animals = max(max_animals, dist[x][y]);
for (int i = 0; i < 4; i++) {
int nx = x + dx[i];
int ny = y + dy[i];
// Check bounds and ignore untouched snow
if (nx >= 0 && nx < r && ny >= 0 && ny < c && g[nx][ny] != '*') {
// 0 cost if same animal type, 1 cost if different
int cost = (g[x][y] == g[nx][ny]) ? 0 : 1;
// If unvisited or we found a cheaper path
if (dist[nx][ny] == -1 || dist[x][y] + cost < dist[nx][ny]) {
dist[nx][ny] = dist[x][y] + cost;
// 0-1 BFS logic: 0-weights to the front, 1-weights to the back
if (cost == 0) {
dq.push_front({nx, ny});
} else {
dq.push_back({nx, ny});
}
}
}
}
}
cout << max_animals << "\n";
return 0;
}
