#include <bits/stdc++.h> using namespace std; #define int long long #define fi first #define se second #define pb push_back mt19937 rng((int)chrono::steady_clock::now().time_since_epoch().count()); vector<pair<int, int>> dir = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}}; int hashp = uniform_int_distribution<int>(10, 1e9)(rng); int hashm1 = 1e9+7; int hashm2 = 1e9+9; int MOD = 1e9+9; int MV = 1e18; void solve(){ int h, w; cin >> h >> w; vector<vector<char>> grid(h, vector<char>(w)); vector<vector<int>> d(h, vector<int>(w, 0)); deque<array<int, 2>> dq; for(int i = 0; i < h; i++){ for(int j = 0; j < w; j++){ cin >> grid[i][j]; } } d[0][0] = 1; dq.pb({0, 0}); int res = 1; while(!dq.empty()){ auto[x, y] = dq.front(); dq.pop_front(); res = max(res, d[x][y]); for(auto[dx, dy]: dir){ int nx = x+dx; int ny = y+dy; if(nx >= 0 && nx < h && ny >= 0 && ny < w && d[nx][ny] == 0 && grid[nx][ny] != '.'){ if(grid[nx][ny] == grid[x][y]){ d[nx][ny] = d[x][y]; dq.push_front({nx, ny}); } else{ d[nx][ny] = d[x][y]+1; dq.pb({nx, ny}); } } } } cout << res; } signed main(){ ios::sync_with_stdio(false); cin.tie(nullptr); solve(); return 0; }