#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=(n)-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x,vector<x>,greater<x>>
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define vtpl(x,y,z) vector<tuple<x,y,z>>
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=1e9+10;
const ll INF=4e18;
const ll dy[9]={0,1,-1,0,1,1,-1,-1,0};
const ll dx[9]={1,0,0,-1,1,-1,1,-1,0};
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
int main(){
    ll h,w;cin >> w >> h;
    vector<string> g(h);rep(i,h)cin >> g[i];
    vvpl st(2);ll now=0;
    rep(i,h){
        rep(j,w){
            if(g[i][j]=='#')continue;
            queue<pl> que;
            que.push({i,j});
            g[i][j]='#';
            while(!que.empty()){
                pl p=que.front();que.pop();
                st[now].pb(p);
                rep(k,4){
                    ll nx=p.fi+dx[k],ny=p.se+dy[k];
                    if(nx<0||ny<0||nx>=h||ny>=w)continue;
                    if(g[nx][ny]=='#')continue;
                    g[nx][ny]='#';
                    que.push({nx,ny});
                }
            }
            now++;
        }
    }
    ll ans=INF;
    for(auto p:st[0]){
        for(auto q:st[1]){
            chmin(ans,abs(p.fi-q.fi)+abs(p.se-q.se));
        }
    }
    cout << ans-1 <<endl;
}