#include <bits/stdc++.h>

using namespace std;

const std::vector<int> dx = {1, -1, 0, 0}, dy = {0, 0, 1, -1};

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int H, W;
  cin >> W >> H;
  int sy = 0, sx = 0;
  vector<string> S(H);
  for (int i = 0; i < H; i++) {
    cin >> S[i];
    for (int j = 0; j < W; j++) {
      if (S[i][j] == '.') {
        sy = i;
        sx = j;
      }
    }
  }
  vector<vector<int>> dist(H, vector<int>(W, -1));
  dist[sy][sx] = 0;
  deque<pair<int, int>> dque;
  dque.push_back(make_pair(sy, sx));
  queue<pair<int, int>> que;
  que.push(make_pair(sy, sx));
  while (!que.empty()) {
    auto q = que.front();
    que.pop();
    int y = q.first, x = q.second;
    for (int i = 0; i < 4; i++) {
      int ny = y + dy[i], nx = x + dx[i];
      if (ny < 0 || ny >= H || nx < 0 || nx >= W) continue;
      if (S[ny][nx] == '#') continue;
      if (dist[ny][nx] != -1) continue;
      dist[ny][nx] = 0;
      que.push(make_pair(ny, nx));
      dque.push_back(make_pair(ny, nx));
    }
  }
  while (!dque.empty()) {
    auto q = dque.front();
    dque.pop_front();
    int y = q.first, x = q.second;
    for (int i = 0; i < 4; i++) {
      int ny = y + dy[i], nx = x + dx[i];
      if (ny < 0 || ny >= H || nx < 0 || nx >= W) continue;
      if (S[ny][nx] == '.' && dist[ny][nx] < 0) {
        cout << dist[y][x] << '\n';
        return 0;
      }
      if (S[ny][nx] == '#' && dist[ny][nx] < 0) {
        dist[ny][nx] = dist[y][x] + 1;
        dque.push_back(make_pair(ny, nx));
      }
    }
  }
  return 0;
}