#include <bits/stdc++.h> #define f first #define s second int main() { int h, w; std::cin >> h >> w; std::vector<std::vector<char>> a(h, std::vector<char>(w)); for (int i = 0; i < h; i++) for (int j = 0; j < w; j++) std::cin >> a[i][j]; std::deque<std::pair<std::pair<int,int>, int>> dq; std::vector<std::vector<int>> dist(h, std::vector<int>(w, -1)); dq.push_front({{0,0},1}); dq.push_front({{0,0},1}); int res = 0; while (!dq.empty()) { auto curr = dq.front(); dq.pop_front(); // lepszy juz zostal ustawiony if (dist[curr.f.f][curr.f.s] != -1) continue; dist[curr.f.f][curr.f.s] = curr.s; res = std::max(res, curr.s); const std::pair<int, int> dirs[4] {{-1, 0}, {1, 0}, {0, -1}, {0, 1}}; for (auto dir : dirs) { int x = curr.f.f + dir.f; int y = curr.f.s + dir.s; if (x >= 0 & y >= 0 && x < h && y < w) { if (dist[x][y] != -1) continue; if (a[x][y] == '.') continue; if (a[curr.f.f][curr.f.s] != a[x][y]) dq.push_back({{x,y}, dist[curr.f.f][curr.f.s]+1}); else dq.push_front({{x, y}, dist[curr.f.f][curr.f.s]}); } } } std::cout << res << '\n'; return 0; }