#define _CRT_SECURE_NO_WARNINGS
//#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> pii;
#define all(c) (c).begin(), (c).end()
#define loop(i,a,b) for(ll i=a; i<ll(b); i++)
#define rep(i,b) loop(i,0,b)
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define mt make_tuple
template<class T> ostream & operator<<(ostream & os, vector<T> const &);
template<int n, class...T> typename enable_if<(n>=sizeof...(T))>::type _ot(ostream &, tuple<T...> const &){}
template<int n, class...T> typename enable_if<(n< sizeof...(T))>::type _ot(ostream & os, tuple<T...> const & t){ os << (n==0?"":" ") << get<n>(t); _ot<n+1>(os, t); }
template<class...T> ostream & operator<<(ostream & os, tuple<T...> const & t){ _ot<0>(os, t); return os; }
template<class T, class U> ostream & operator<<(ostream & os, pair<T,U> const & p){ return os << "(" << p.first << ", " << p.second << ") "; }
template<class T> ostream & operator<<(ostream & os, vector<T> const & v){ rep(i,v.size()) os << v[i] << (i+1==(int)v.size()?"":" "); return os; }
#ifdef DEBUG
#define dump(...) (cerr<<#__VA_ARGS__<<" = "<<mt(__VA_ARGS__)<<" ["<<__LINE__<<"]"<<endl)
#else
#define dump(...)
#endif

typedef int Weight;
struct Edge {
    int src, dst;
    Weight weight;
    Edge(int src_, int dst_, Weight weight_) :
        src(src_), dst(dst_), weight(weight_) { }
};
bool operator < (const Edge &e, const Edge &f) {
    return e.weight != f.weight ? e.weight > f.weight : // !!INVERSE!!
        e.src != f.src ? e.src < f.src : e.dst < f.dst;
}
typedef vector<Edge> Edges;
typedef vector<Edges> Graph;
typedef vector<Weight> Array;
typedef vector<Array> Matrix;

int const inf = 10000000;
void dijkstra(Graph const & g, int s, vector<Weight> &dist) {
    typedef tuple<Weight,int> State;
    priority_queue<State> q;
    dist.assign(g.size(), inf); dist[s] = 0;
    q.emplace(0,s);
    while (q.size()) {
        Weight d;
        int v;
        tie(d,v) = q.top(); q.pop();
        d *= -1;
        if (dist[v] < d) continue;
        rep(i,g[v].size()){
            const Edge &e = g[v][i];
            if (dist[e.dst] > dist[v] + e.weight) {
                dist[e.dst] = dist[v] + e.weight;
                q.emplace(-dist[e.dst], e.dst);
            }
        }
    }
}

char grid[30][30];
int W,H;
int f(int i, int j){
    return i*W+j;
}

int main(){
    while(cin >> W >> H){
        Graph g(H*W);
        rep(i,H) cin >> grid[i];
        int dx[] = {0,1,0,-1};
        int dy[] = {1,0,-1,0};
        rep(i,H)rep(j,W){
            rep(d,4){
                int ni = i+dy[d];
                int nj = j+dx[d];
                if(ni < 0 || nj < 0) break;
                if(ni >= H || nj >= W) break;
                if(grid[ni][nj] == '#'){
                    g[f(i,j)].eb(f(i,j),f(ni,nj),1);
                } else {
                    g[f(i,j)].eb(f(i,j),f(ni,nj),0);
                }
            }
        }
        int ans = 1000000000;
        rep(i,H)rep(j,W){
            rep(ii,H)rep(jj,W){
                if(grid[i][j]=='.' && grid[ii][jj]=='.'){
                    vi v;
                    dijkstra(g,f(i,j),v);
                    int x = v[f(ii,jj)];
                    if(x==0) continue;
                    ans = min(ans,x);
                }
            }
        }
        cout << ans << endl;
    }
}