#include <cassert>// c
#include <iostream>// io
#include <iomanip>
#include <fstream>
#include <sstream>
#include <vector>// container
#include <map>
#include <set>
#include <queue>
#include <bitset>
#include <stack>
#include <list>
#include <algorithm>// other
#include <complex>
#include <numeric>
#include <functional>
#include <random>
#include <regex>
using namespace std;
 
typedef long long ll;
typedef unsigned long long ull;
 
#define ALL(c) c.begin(),c.end()
#define REP(i,n) FOR(i,0,n)
#define REPr(i,n) FORr(i,0,n)
#define FOR(i,l,r) for(int i=(int)(l);i<(int)(r);++i)
#define FORr(i,l,r) for(int i=(int)(r)-1;i>=(int)(l);--i)
// #define EACH(it,o) for(auto it = (o).begin(); it != (o).end(); ++it)
#define IN(l,v,r) ((l)<=(v) && (v)<(r))
#define UNIQUE(v) v.erase(unique(ALL(v)),v.end())
//debug
#define DUMP(x)  cerr << #x << " = " << (x)
#define LINE()    cerr<< " (L" << __LINE__ << ")"
 
class range{
private:
	struct Iter{
		int v;
		int operator*(){return v;}
		bool operator!=(Iter& itr) {return v < itr.v;}
		void operator++() {++v;}
	};
	Iter i, n;
public:
	range(int n) : i({0}), n({n}) {}
	range(int i, int n) : i({i}), n({n}) {}
	Iter& begin() {return i;}
	Iter& end() {return n;}
};
 
//input
template<typename T1,typename T2> istream& operator >> (istream& is,pair<T1,T2>& p){return is>>p.first>>p.second;}
template<typename T1> istream& operator >> (istream& is,tuple<T1>& t){return is >> get<0>(t);}
template<typename T1,typename T2> istream& operator >> (istream& is,tuple<T1,T2>& t){return is >> get<0>(t) >> get<1>(t);}
template<typename T1,typename T2,typename T3> istream& operator >> (istream& is,tuple<T1,T2,T3>& t){return is >>get<0>(t)>>get<1>(t)>>get<2>(t);}
template<typename T1,typename T2,typename T3,typename T4> istream& operator >> (istream& is,tuple<T1,T2,T3,T4>& t){return is >> get<0>(t)>>get<1>(t)>>get<2>(t)>>get<3>(t);}
template<typename T1,typename T2,typename T3,typename T4,typename T5> istream& operator >> (istream& is, const tuple<T1,T2,T3,T4,T5>& t){return is >> get<0>(t) >> get<1>(t) >> get<2>(t) >> get<3>(t) >> get<4>(t);}
template<typename T1,typename T2,typename T3,typename T4,typename T5,typename T6> istream& operator >> (istream& is, const tuple<T1,T2,T3,T4,T5,T6>& t){return is >> get<0>(t) >> get<1>(t) >> get<2>(t) >> get<3>(t) >> get<4>(t) >> get<5>(t);}
template<typename T1,typename T2,typename T3,typename T4,typename T5,typename T6,typename T7> istream& operator >> (istream& is, const tuple<T1,T2,T3,T4,T5,T6,T7>& t){return is >> get<0>(t) >> get<1>(t) >> get<2>(t) >> get<3>(t) >> get<4>(t) >> get<5>(t) >> get<6>(t);}
template<typename T> istream& operator >> (istream& is,vector<T>& as){for(int i:range(as.size()))is >>as[i];return is;}
 
//output
template<typename T> ostream& operator << (ostream& os, const set<T>& ss){for(auto a:ss){if(a!=ss.begin())os<<" "; os<<a;}return os;}
template<typename T1,typename T2> ostream& operator << (ostream& os, const pair<T1,T2>& p){return os<<p.first<<" "<<p.second;}
template<typename K,typename V> ostream& operator << (ostream& os, const map<K,V>& m){bool isF=true;for(auto& p:m){if(!isF)os<<endl;os<<p;isF=false;}return os;}
template<typename T1> ostream& operator << (ostream& os, const tuple<T1>& t){return os << get<0>(t);}
template<typename T1,typename T2> ostream& operator << (ostream& os, const tuple<T1,T2>& t){return os << get<0>(t)<<" "<<get<1>(t);}
template<typename T1,typename T2,typename T3> ostream& operator << (ostream& os, const tuple<T1,T2,T3>& t){return os << get<0>(t)<<" "<<get<1>(t)<<" "<<get<2>(t);}
template<typename T1,typename T2,typename T3,typename T4> ostream& operator << (ostream& os, const tuple<T1,T2,T3,T4>& t){return os << get<0>(t)<<" "<<get<1>(t)<<" "<<get<2>(t)<<" "<<get<3>(t);}
template<typename T1,typename T2,typename T3,typename T4,typename T5> ostream& operator << (ostream& os, const tuple<T1,T2,T3,T4,T5>& t){return os << get<0>(t)<<" "<<get<1>(t)<<" "<<get<2>(t)<<" "<<get<3>(t)<<" "<<get<4>(t);}
template<typename T1,typename T2,typename T3,typename T4,typename T5,typename T6> ostream& operator << (ostream& os, const tuple<T1,T2,T3,T4,T5,T6>& t){return os << get<0>(t)<<" "<<get<1>(t)<<" "<<get<2>(t)<<" "<<get<3>(t)<<" "<<get<4>(t)<<" "<<get<5>(t);}
template<typename T1,typename T2,typename T3,typename T4,typename T5,typename T6,typename T7> ostream& operator << (ostream& os, const tuple<T1,T2,T3,T4,T5,T6,T7>& t){return os << get<0>(t)<<" "<<get<1>(t)<<" "<<get<2>(t)<<" "<<get<3>(t)<<" "<<get<4>(t)<<" "<<get<5>(t)<<" "<<get<6>(t);}
template<typename T> ostream& operator << (ostream& os, const vector<T>& as){for(int i:range(as.size())){if(i!=0)os<<" "; os<<as[i];}return os;}
template<typename T> ostream& operator << (ostream& os, const vector<vector<T>>& as){for(int i:range(as.size())){if(i!=0)os<<endl; os<<as[i];}return os;}
 
// values
template<typename T> inline T INF(){assert(false);};
template<> inline int INF<int>(){return 1<<28;};
template<> inline ll INF<ll>(){return 1LL<<58;};
template<> inline double INF<double>(){return 1e16;};
template<> inline long double INF<long double>(){return 1e16;};
 
template<class T> inline T EPS(){assert(false);};
template<> inline int EPS<int>(){return 1;};
template<> inline ll EPS<ll>(){return 1LL;};
template<> inline double EPS<double>(){return 1e-8;};
template<> inline long double EPS<long double>(){return 1e-8;};
 
// min{2^r | n < 2^r}
template<typename T> T upper_pow2(T n){
	T res=1;while(res<n)res<<=1;return res;
}
// max{d | 2^d  <= n}
template<typename T> T msb(T n){
	int d=30;while((1<<d)>n)d--;return d;
}
 
template<typename T,typename U> T pmod(T v,U M){return (v%M+M)%M;}

struct UnionFind{
    vector<int> par,rank,ss;
    int size;
    UnionFind(int n):size(n){
        par=vector<int>(n);iota(ALL(par),0);
        rank = vector<int>(n);ss=vector<int>(n,1);
    }
    int root(int x){ return par[x] = par[x] == x ? x: root(par[x]);}
    bool same(int x,int y){ return root(x) == root(y);}
    void unite(int x,int y){
        x = root(x);y = root(y);
        if(x==y)return;
        if(rank[x]>rank[y])swap(x,y);
        par[x] = y;ss[y]+=ss[x];
        if(rank[x] == rank[y]) rank[x]++;
        size--;
    }
    int getS(int x){ return ss[root(x)];}
};

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

class Main{
	public:

	void run(){
		int W,H;cin >> W >> H;
		vector<string> board(H);cin >> board;

		UnionFind uf(H*W);
		for(int y=0;y<H;y++)for(int x=0;x<W;x++){
			for(int d=0;d<4;d++){
				int ny=y+dy[d],nx=x+dx[d];
				if(!IN(0,ny,H) || !IN(0,nx,W))continue;
				if(board[y][x]=='.' && board[ny][nx]=='.'){
					uf.unite(y*W+x,ny*W+nx);
				}
			}
		}

			
		int mv=INF<int>();
		for(int y1=0;y1<H;y1++)for(int x1=0;x1<W;x1++)if(board[y1][x1]=='.')
		for(int y2=0;y2<H;y2++)for(int x2=0;x2<W;x2++)if(board[y2][x2]=='.'){
			if(!uf.same(y1*W+x1,y2*W+x2))
				mv=min(mv,abs(x1-x2)+ abs(y1-y2)-1);
		}

		cout << mv <<endl;

	}
};

int main(){
	cout <<fixed<<setprecision(20);
	cin.tie(0);
	ios::sync_with_stdio(false);
	Main().run();
	return 0;
}