#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
using namespace std;
using std::cout;
using std::cin;
using std::endl;
using ll=long long;
using ld=long double;
const ll ILL=2167167167167167167;
const int INF=2100000000;
const int mod=998244353;
#define rep(i,a,b) for (int i=(int)(a);i<(int)(b);i++)
#define all(p) p.begin(),p.end()
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,const T &b){if(a>b){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
void yneos(bool a){if(a) cout<<"Yes\n"; else cout<<"No\n";}
template<class T> void vec_out(vector<T> &p){for(int i=0;i<(int)(p.size());i++){if(i) cout<<" ";cout<<p[i];}cout<<"\n";}
template<class T> T vec_min(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmin(ans,x);return ans;}
template<class T> T vec_max(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmax(ans,x);return ans;}
template<class T> T vec_sum(vector<T> &a){assert(!a.empty());T ans=a[0]-a[0];for(auto &x:a) ans+=x;return ans;}
int pop_count(long long a){int res=0;while(a){res+=(a&1),a>>=1;}return res;}



void solve();
// oddloop
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	
	int t=1;
	//cin>>t;
	rep(i,0,t) solve();
}

void solve(){
	int H,W;
	cin>>H>>W;
	vector<string> p(H);
	rep(i,0,H) cin>>p[i];
	vector<vector<int>> q(H,vector<int>(W));
	rep(i,1,H-1) rep(j,1,W-1) rep(k,-1,2) rep(l,-1,2) if(p[i+k][j+l]=='#') q[i][j]=1;
	vector<pair<int,int>> order;
	vector seen(H,vector<int>(W,INF));
	rep(i,1,H) order.push_back({i,0}),seen[i][0]=0;
	rep(j,1,W-1) order.push_back({H-1,j}),seen[H-1][j]=0;
	vector<int> dx={0,0,1,-1,1,1,-1,-1},dy={1,-1,0,-1,1,-1,1,-1};
	int A=0;
	while(!order.empty()){
		vector<pair<int,int>> n_order;
		rep(i,0,order.size()){
			auto [x,y]=order[i];
			if(seen[x][y]!=A) continue;
			rep(k,0,8){
				int s=x+dx[k],t=dy[k]+y;
				if(min(s,t)==-1||s==H||t==W) continue;
				if(s+t==0||s+t+2==H+W) continue;
				if(q[s][t]){
					if(chmin(seen[s][t],A)) order.push_back({s,t});
				}
				else{
					rep(a,-2,3) rep(b,-2,3){
						int c=a+s,d=b+t;
						if(min(c,d)<=-1||c>=H||d>=W) continue;
						if(c+d==0||c+d+2==H+W) continue;
						if(chmin(seen[c][d],A+1)){
							n_order.push_back({c,d});
						}
					}
				}
			}
		}
		swap(n_order,order);
		A++;
	}
	/*
	rep(i,0,H){
		rep(j,0,W) cout<<seen[i][j];
		cout<<endl;
	}*/
	int ans=INF;
	rep(j,1,W) chmin(ans,seen[1][j]);
	rep(i,1,H-1) chmin(ans,seen[i][W-2]);
	cout<<ans<<"\n";
}