#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

int dx[4] = {-1, 1, 0, 0};
int dy[4] = {0, 0, -1, 1};

int main() {
    int w, h;
    cin >> w >> h;
    string s[h];
    rep(i,h)cin >> s[i];

    vector<P> u,v;
    int num = 0;

    rep(i,h){
        rep(j,w){
            if(s[i][j] == '.'){
                queue<P> que;
                que.push(P(i,j));
                if(num == 0) u.push_back(P(i,j));
                else v.push_back(P(i,j));
                s[i][j] = '#';
                while(que.size()>0){
                    int x = que.front().first;
                    int y = que.front().second;
                    que.pop();
                    rep(k,4){
                        int nx = x + dx[k];
                        int ny = y + dy[k];
                        if(s[nx][ny] == '.'){
                            if(num == 0) u.push_back(P(nx,ny));
                            else v.push_back(P(nx,ny));
                            que.push(P(nx,ny));
                        }
                        s[nx][ny] = '#';
                    }
                }
                num++;
            }
        }
    }

    int ans = 1001001;
    rep(i,u.size()){
        rep(j,v.size()){
            int tmp = abs(u[i].first - v[j].first) + abs(u[i].second - v[j].second);
            ans = min(ans, tmp);
        }
    }

    cout << ans - 1 << endl;
    return 0;
}