#include <iostream>
#include <vector>
#include <string>
#include <deque>
#include <tuple>
int main() {
int h, w;
std::cin >> h >> w;
std::vector<std::string> grid(h);
for (auto& s : grid) std::cin >> s;
int ans = 1;
int dr[4] = {1, 0, -1, 0};
int dc[4] = {0, 1, 0, -1};
int cur = 0;
std::deque<std::tuple<int, int>> que[2];
std::vector<std::vector<bool>> vis(h, std::vector<bool>(w));
que[cur].emplace_back(0, 0), vis[0][0] = true;
while (not que[cur].empty() or not que[cur^1].empty()) {
if (que[cur].empty()) {
cur ^= 1, ++ans;
}
auto [r, c] = que[cur].front();
que[cur].pop_front();
for (int k = 0; k < 4; ++k) {
int nr = r + dr[k];
int nc = c + dc[k];
if (nr < 0 or h <= nr
or nc < 0 or w <= nc
or vis[nr][nc]
or '.' == grid[nr][nc]) continue;
int nq = cur ^ (grid[nr][nc] != grid[r][c]);
que[nq].emplace_back(nr, nc);
vis[nr][nc] = true;
}
}
std::cout << ans << "\n";
}
