// what is matter? never mind. 
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,sse4,popcnt,abm,mmx,avx,avx2") 
#include<bits/stdc++.h>
#define For(i,a,b) for(int i=(a);i<=(b);++i)
#define Rep(i,a,b) for(int i=(a);i>=(b);--i)
#define ll long long
#define ull unsigned long long
#define i128 __int128
using namespace std;
inline int read()
{
	char c=getchar();int x=0;bool f=0;
	for(;!isdigit(c);c=getchar())f^=!(c^45);
	for(;isdigit(c);c=getchar())x=(x<<1)+(x<<3)+(c^48);
	if(f)x=-x;return x;
}

#define mod 998244353
struct modint{
	int x;
	modint(int o=0){x=o;}
	modint &operator = (int o){return x=o,*this;}
	modint &operator +=(modint o){return x=x+o.x>=mod?x+o.x-mod:x+o.x,*this;}
	modint &operator -=(modint o){return x=x-o.x<0?x-o.x+mod:x-o.x,*this;}
	modint &operator *=(modint o){return x=1ll*x*o.x%mod,*this;}
	modint &operator ^=(int b){
		modint a=*this,c=1;
		for(;b;b>>=1,a*=a)if(b&1)c*=a;
		return x=c.x,*this;
	}
	modint &operator /=(modint o){return *this *=o^=mod-2;}
	friend modint operator +(modint a,modint b){return a+=b;}
	friend modint operator -(modint a,modint b){return a-=b;}
	friend modint operator *(modint a,modint b){return a*=b;}
	friend modint operator /(modint a,modint b){return a/=b;}
	friend modint operator ^(modint a,int b){return a^=b;}
	friend bool operator ==(modint a,int b){return a.x==b;}
	friend bool operator !=(modint a,int b){return a.x!=b;}
	bool operator ! () {return !x;}
	modint operator - () {return x?mod-x:0;}
	bool operator <(const modint&b)const{return x<b.x;}
};
inline modint qpow(modint x,int y){return x^y;}

vector<modint> fac,ifac,iv;
inline void initC(int n)
{
	if(iv.empty())fac=ifac=iv=vector<modint>(2,1);
	int m=iv.size(); ++n;
	if(m>=n)return;
	iv.resize(n),fac.resize(n),ifac.resize(n);
	For(i,m,n-1){
		iv[i]=iv[mod%i]*(mod-mod/i);
		fac[i]=fac[i-1]*i,ifac[i]=ifac[i-1]*iv[i];
	}
}
inline modint C(int n,int m){
	if(m<0||n<m)return 0;
	return initC(n),fac[n]*ifac[m]*ifac[n-m];
}
inline modint sign(int n){return (n&1)?(mod-1):(1);}

#define fi first
#define se second
#define pb push_back
#define mkp make_pair
typedef pair<int,int>pii;
typedef vector<int>vi;

#define maxn 500005
#define inf 0x3f3f3f3f

int h,w,n;
string mp[2005];
int P(int i,int j){
	return (i-1)*w+j;
}

vi e[maxn];
vector<pii>E;

int fa1[maxn],dis1[maxn],fan[maxn],disn[maxn];
void dfs(int u,int *f,int *d){
	for(int v:e[u])
		if(v!=f[u])f[v]=u,d[v]=d[u]+1,dfs(v,f,d);
}
int t[maxn],len;

signed main()
{
	h=read(),w=read(),n=h*w;
	For(i,0,h*2)cin>>mp[i];
	// heng
	For(i,1,h){
		For(j,1,w-1){
			int u=P(i,j),v=P(i,j+1);
			char ch=mp[i*2-1][j*2];
			if(ch=='.')e[u].pb(v),e[v].pb(u);//cout<<"Add "<<u<<" "<<v<<"\n";
			else E.pb(mkp(u,v));
		}
	}
	For(i,1,h-1){
		For(j,1,w){
			int u=P(i,j),v=P(i+1,j);
			char ch=mp[i*2][j*2-1];
			if(ch=='.')e[u].pb(v),e[v].pb(u);//cout<<"Add "<<u<<" "<<v<<"\n";
			else E.pb(mkp(u,v));
		}
	}
	dfs(1,fa1,dis1);
	dfs(n,fan,disn);
	int res=dis1[n];
	for(auto [u,v]:E){
		int du=(dis1[u]+disn[u]-dis1[n])/2;
		int pu=dis1[u]-du;
		int dv=(dis1[v]+disn[v]-dis1[n])/2;
		int pv=dis1[v]-dv;
		if(pu==pv)continue;
		if(pu>pv)swap(pu,pv),swap(u,v);
	//	cout<<"u,v "<<u<<" "<<v<<" "<<dis1[u]<<" "<<disn[v]<<"\n";
		res=max(res,dis1[u]+1+disn[v]);
	}
	cout<<res+1;
	return 0;
}