#include <bits/stdc++.h> #include <ext/pb_ds/assoc_container.hpp> #include <ext/pb_ds/tree_policy.hpp> using namespace std; using namespace __gnu_pbds; #define solveT() {int t; cin >> t; while (t--) solve();}; #define int long long template <typename T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>; void solve() { int h, w; cin >> h >> w; vector<string> arr(h); for (int i = 0; i < h; i++) { cin >> arr[i]; } vector<pair<int, int>> dr = {{-1, 0}, {0, -1}, {1, 0}, {0, 1}}; vector<vector<bool>> vis(h, vector<bool>(w, false)); vector<vector<int>> depth(h, vector<int>(w, -1)); auto bfs = [&](int i, int j) { deque<pair<int, int>> q; q.emplace_front(i, j); depth[i][j] = 1; int ans{0}; while (!q.empty()) { auto [x, y] = q.front(); q.pop_front(); ans = max(ans, depth[x][y]); for (auto [dx, dy] : dr) { if (x + dx >= 0 && x + dx < h && y + dy >= 0 && y + dy < w && arr[x + dx][y + dy] != '.' && !vis[x + dx][y + dy]) { vis[x + dx][y + dy] = true; if (arr[x][y] == arr[x + dx][y + dy]) { q.emplace_front(x + dx, y + dy); depth[x + dx][y + dy] = depth[x][y]; } else { q.emplace_back(x + dx, y + dy); depth[x + dx][y + dy] = 1 + depth[x][y]; } } } } return ans; }; cout << bfs(0, 0) << endl; } signed main() { ios_base::sync_with_stdio(false); cin.tie(NULL); //freopen("file.in", "r", stdin); //freopen("file.out", "w", stdout); solve(); return 0; }