#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0; i < (n);i++)
#define sz(x) int(x.size())
typedef long long ll;
typedef pair<int,int> P;

const int INF = 1e9;

int dy[] = {1,0,-1,0};
int dx[] = {0,1,0,-1};

int main(){
  int h, w;
  cin >> w >> h;
  vector<vector<char>> g(h,vector<char>(w));
  int sy, sx;
  rep(i,h) rep(j,w) {
    cin >> g[i][j];
    if (g[i][j] == '.') sy = i, sx = j;
  }
  vector<vector<int>> dist(h,vector<int>(w,INF));
  int res = INF;
  deque<P> deq;
  deq.push_front({sy,sx});
  dist[sy][sx] = 0;
  while (!deq.empty()) {
    P p = deq.front(); deq.pop_front();  
    rep(i,4) {
      int ny = p.first + dy[i];
      int nx = p.second + dx[i];
      if (ny < 0 || nx < 0 || nx >= w-1 || ny >= h-1) continue;
      if (dist[ny][nx] != INF) continue;
      if (g[ny][nx] == '.') {
        if (g[p.first][p.second] == '#') res = min(res,dist[p.first][p.second]);
        dist[ny][nx] = 0;
        deq.push_front({ny,nx});
      } else {
        dist[ny][nx] = dist[p.first][p.second] + 1;
        deq.push_back({ny,nx});
      }
    }
  }
  
  cout << res << endl;
  return 0;
}