/** * Author: wannaStayWithU * Date: 2/2/2569 */ #include <bits/stdc++.h> using namespace std; signed main() { ios_base::sync_with_stdio(false); cin.tie(0); int n, m; cin >> n >> m; char arr[n][m]; int dp[n][m]; for (int i = 0; i < n; i++) { for (int j = 0; j < m; j++) { cin >> arr[i][j]; dp[i][j] = 1e9; } } dp[0][0] = 1; deque<pair<int, int>> qu; qu.push_front({0, 0}); int di[4] = {1, -1, 0, 0}; int dj[4] = {0, 0, -1, 1}; while (qu.size()) { auto [u, v] = qu.front(); qu.pop_front(); for (int p = 0; p < 4; p++) { int du = u + di[p]; int dv = v + dj[p]; if (du < 0 || du >= n || dv < 0 || dv >= m) continue; if (arr[du][dv] == '.' || dp[du][dv] != 1e9) continue; if (arr[du][dv] == arr[u][v]) dp[du][dv] = dp[u][v], qu.push_front({du, dv}); else dp[du][dv] = dp[u][v] + 1, qu.push_back({du, dv}); } } int ans = 0; for (int i = 0; i < n; i++) { for (int j = 0; j < m; j++) { if (dp[i][j] != 1e9) ans = max(ans, dp[i][j]); } } cout << ans; return 0; } /* */