#include<bits/stdc++.h>
#include<atcoder/all>
using namespace std;
using namespace atcoder;
typedef long long int ll;
typedef long double ld;
#define FOR(i,l,r) for(ll i=l;i<r;i++)
#define REP(i,n) FOR(i,0,n)
#define RFOR(i,l,r) for(ll i=r-1;i>=l;i--)
#define RREP(i,n) RFOR(i,0,n)
#define ALL(x) x.begin(),x.end()
#define PA pair<ll,ll>
#define F first
#define S second
#define BS(A,x) binary_search(ALL(A),x)
#define LB(A,x) (ll)(lower_bound(ALL(A),x)-A.begin())
#define UB(A,x) (ll)(upper_bound(ALL(A),x)-A.begin())
#define COU(A,x) (UB(A,x)-LB(A,x))
#define sz(c) ((ll)(c).size())
//#include<boost/multiprecision/cpp_int.hpp>
//namespace mp=boost::multiprecision;
//using Bint=mp::cpp_int;
template<typename T>using min_priority_queue=priority_queue<T,vector<T>,greater<T>>;
template<typename T1,typename T2>ostream&operator<<(ostream&os,pair<T1,T2>&p){os<<p.F<<" "<<p.S;return os;}
template<typename T1,typename T2>istream&operator>>(istream&is,pair<T1,T2>&p){is>>p.F>>p.S;return is;}
template<typename T>ostream&operator<<(ostream&os,vector<T>&v){REP(i,sz(v))os<<v[i]<<(i+1!=sz(v)?" ":"");return os;}
template<typename T>istream&operator>>(istream&is,vector<T>&v){for(T&in:v)is>>in;return is;}
template<class T>bool chmax(T&a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T>bool chmin(T&a,T b){if(b<a){a=b;return 1;}return 0;}
ld dist(ld x1,ld y1,ld x2,ld y2){return sqrtl((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));}
//using mint=modint1000000007;
using mint=modint998244353;
//const ll mod=1000000007;
const ll mod=998244353;
//using mint=modint;
ostream&operator<<(ostream&os,mint&a){os<<a.val();return os;}
int main(){
  ll W,H;cin>>W>>H;
  vector<string>S(H);cin>>S;
  vector<vector<ll>>DP(H,vector<ll>(W,1e18)),m={{1,0},{0,1},{-1,0},{0,-1}};
  REP(i,H)REP(j,W)if(S[i][j]=='.'){
    if(DP[i][j]==1e18){
        queue<ll>X,Y;
        X.emplace(i);Y.emplace(j);
        DP[i][j]=0;
        while(sz(X)){
            ll x=X.front(),y=Y.front();
            X.pop();Y.pop();
            REP(_,4){
                ll dx=x+m[_][0],dy=y+m[_][1];
                if(min({dx,H-1-dx,dy,W-1-dy})<0)continue;
                if(chmin(DP[dx][dy],DP[x][y]+(S[dx][dy]=='#'))){X.emplace(dx);Y.emplace(dy);}
            }
        }
    }
    else if(DP[i][j]){cout<<DP[i][j]<<endl;return 0;}
  }
  return 0;
}