#include <bits/stdc++.h> using namespace std; vector<string> matrix; vector<vector<int>> dir{{1, 0}, {-1, 0}, {0, 1}, {0, -1}}; int inside(int x, int y, int h, int w) { return x >= 0 and x < h and y >= 0 and y < w and matrix[x][y] != '.'; } int main() { int h, w; cin >> h >> w; matrix.resize(h); for(int i = 0; i < h; i++) { cin >> matrix[i]; } deque<pair<int, int>> q; vector<vector<int>> cost(h, vector<int>(w, INT_MAX)); q.push_front({0, 0}); cost[0][0] = 1; int maxVal = 1; while(!q.empty()) { int x = q.front().first; int y = q.front().second; q.pop_front(); for(int i = 0; i < 4; i++) { int nx = x + dir[i][0]; int ny = y + dir[i][1]; if(inside(nx, ny, h, w) and cost[nx][ny] == INT_MAX) { if(matrix[nx][ny] == matrix[x][y]) { q.push_front({nx, ny}); cost[nx][ny] = cost[x][y]; } else { q.push_back({nx, ny}); cost[nx][ny] = cost[x][y] + 1; } maxVal = max(maxVal, cost[nx][ny]); } } } cout << maxVal << endl; }