#include <bits/stdc++.h>
//#include<boost/multiprecision/cpp_int.hpp>
//#include<boost/multiprecision/cpp_dec_float.hpp>
//#include <atcoder/all>
#define rep(i, a) for (int i = (int)0; i < (int)a; ++i)
#define rrep(i, a) for (int i = (int)a - 1; i >= 0; --i)
#define REP(i, a, b) for (int i = (int)a; i < (int)b; ++i)
#define RREP(i, a, b) for (int i = (int)a - 1; i >= b; --i)
#define repl(i, a) for (ll i = (ll)0; i < (ll)a; ++i)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define popcount __builtin_popcount
#define fi first
#define se second
using ll = long long;
constexpr ll mod = 1e9 + 7;
constexpr ll mod_998244353 = 998244353;
constexpr ll INF = 1LL << 60;

// #pragma GCC target("avx2")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")

//using lll=boost::multiprecision::cpp_int;
//using Double=boost::multiprecision::number<boost::multiprecision::cpp_dec_float<1024>>;//仮数部が1024桁
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;
}

template <typename T>
T mypow(T x, T n, const T &p = -1)
{ //x^nをmodで割った余り

	if (p != -1)
	{
		x %= p;
	}
	T ret = 1;
	while (n > 0)
	{
		if (n & 1)
		{
			if (p != -1)
				ret = (ret * x) % p;
			else
				ret *= x;
		}
		if (p != -1)
			x = (x * x) % p;
		else
			x *= x;
		n >>= 1;
	}
	return ret;
}

using namespace std;
//using namespace atcoder;

using P=pair<int,int>;
int nx[]={1,0,-1,0},ny[]={0,1,0,-1};
void solve()
{
	int w,h;
	cin>>w>>h;
	vector<string>s(h);
	rep(i,h)cin>>s[i];
	int x,y;
	auto func=[&s,h,w,&x,&y]()->void{
		rep(i,h){
			rep(j,w){
				if(s[i][j]=='.'){
					x=i,y=j;
					return;
				}
			}
		}
	};
	func();
	queue<P>q;
	q.emplace(x,y);
	s[x][y]='s';
	while(!q.empty()){
		auto p=q.front();
		q.pop();
		rep(i,4){
			int xx=p.fi+nx[i],yy=p.se+ny[i];
			if(xx>=0&&xx<h&&yy>=0&&yy<w){
				if(s[xx][yy]=='.'){
					s[xx][yy]='s';
					q.emplace(xx,yy);
				}
			}
		}
	}
	vector<vector<int>>dis(h,vector<int>(w,500));
	rep(i,h)rep(j,w)if(s[i][j]=='s')q.emplace(i,j),dis[i][j]=0;
	int ans=500;
	while(!q.empty()){
		auto p=q.front();
		q.pop();
		rep(i,4){
			int xx=p.fi+nx[i],yy=p.se+ny[i];
			if(xx>=0&&xx<h&&yy>=0&&yy<w){
				if(dis[xx][yy]==500&&s[xx][yy]=='#'){
					dis[xx][yy]=dis[p.fi][p.se]+1;
					q.emplace(xx,yy);
				}else if(s[xx][yy]=='.'){
					chmin(ans,dis[p.fi][p.se]);
				}
			}
		}
	}
	cout<<ans<<"\n";
}

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cout << fixed << setprecision(15);
	solve();
	return 0;
}