#include <bits/stdc++.h>
using namespace std;

#define int long long
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define repi(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define all(x) (x).begin(),(x).end()
#define pb push_back
#define mp make_pair
#define mt make_tuple

typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;

const int inf = 1LL<<60;
const int mod = 1e9 + 7;
const double eps = 1e-9;

/*{
}*/

class UnionFind
{
public:
  int n;
  vector<int> par, rnk;

  UnionFind(int n_)
  {
    n = n_;
    par.resize(n);
    rnk.resize(n);
    for(int i = 0; i < n; i++){
      par[i] = i;
      rnk[i] = 0;
    }
  }

  int find(int x)
  {
    if(par[x] == x) return x;
    return par[x] = find(par[x]);
  }

  void unite(int x, int y)
  {
    x = find(x);
    y = find(y);
    if(x == y) return;

    if(rnk[x] < rnk[y]){
      par[x] = y;
    }else{
      par[y] = x; 
      if(rnk[x] == rnk[y]) rnk[x]++;
    }
  }

  bool same(int x, int y)
  {
    return find(x) == find(y);
  }
};

signed main()
{
  int w, h;
  cin >> w >> h;

  string s[h];
  rep(i, h) cin >> s[i];

  UnionFind uf(h*w);
  rep(y, h) rep(x, w){
    if(s[y][x] == '.'){
      if(x+1 < w and s[y][x+1] == '.') uf.unite(y*w+x, y*w+x+1);
      if(y+1 < h and s[y+1][x] == '.') uf.unite(y*w+x, (y+1)*w+x);
    }
  }

  int ans = inf;
  rep(y1, h) rep(x1, w) rep(y2, h) rep(x2, w){
    if(s[y1][x1] != '.' or s[y2][x2] != '.') continue;
    if(!uf.same(y1*w+x1, y2*w+x2)){
      int dist = max(0LL, abs(x1-x2) + abs(y1-y2)-1);
      if(ans > dist){
//        printf("%lld %lld %lld %lld\n", y1, x1, y2, x2);
      }
      ans = min(ans, dist);
    }
  }

  cout << ans << endl;

  return 0;
}