#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp> 

using namespace std;
using namespace __gnu_pbds; 

#define ff              first
#define ss              second
#define ll              int64_t
#define ld              long double
#define nl              cout<<"\n"
#define all(v)          v.begin(),v.end()
#define mset(a,v)       memset((a),(v),sizeof(a))
#define forn(i,a,b)     for(int64_t i=int64_t(a);i<int64_t(b);++i)
#define forb(i,a,b)     for(int64_t i=int64_t(a);i>=int64_t(b);--i)
#define fastio()        ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define ordered_set     tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> 

#define mod         1000000007
#define mod2        998244353 
#define inf         1000000000000007
#define pi          3.14159265358979323846

template<class L,class R> ostream& operator<<(ostream& out,pair<L,R> &p)        {return out<<"("<<p.ff<<", "<<p.ss<<")";}
template<class T> ostream& operator<<(ostream& out,vector<T> &v)                {out<<"[";for(auto it=v.begin();it!=v.end();++it){if(it!=v.begin())out<<", ";out<<*it;}return out<<"]";}
template<class T> ostream& operator<<(ostream& out,deque<T> &v)                 {out<<"[";for(auto it=v.begin();it!=v.end();++it){if(it!=v.begin())out<<", ";out<<*it;}return out<<"]";}
template<class T> ostream& operator<<(ostream& out,set<T> &s)                   {out<<"{";for(auto it=s.begin();it!=s.end();++it){if(it!=s.begin())out<<", ";out<<*it;}return out<<"}";}
template<class L,class R> ostream& operator<<(ostream& out,map<L,R> &m)         {out<<"{";for(auto it=m.begin();it!=m.end();++it){if(it!=m.begin())out<<", ";out<<*it;}return out<<"}";}

void dbg_out() {cerr<<"]\n";}
template<typename Head,typename... Tail> 
void dbg_out(Head H,Tail... T) {cerr<<H;if(sizeof...(Tail))cerr<<", ";dbg_out(T...);}
#ifdef LOCAL
	#define dbg(...) cerr<<"["<<#__VA_ARGS__<<"] = [",dbg_out(__VA_ARGS__)
#else
	#define dbg(...)
#endif

ll count_digits(ll n)   {ll dig=floor(log10(n)+1);return dig;}
ll mpow(ll x,ll y,ll p) {ll r=1;x=x%p;while(y>0){if(y&1)r=(r*x)%p;y=y>>1;x=(x*x)%p;}return r;} 
ll mod_inv(ll a,ll m)   {ll m0=m,y=0,x=1;if(m==1)return 0;while(a>1){ll q=a/m,t=m;m=a%m,a=t;t=y;y=x-q*y;x=t;}if(x<0)x+=m0;return x;} 
/* const ll MAXN=1000007;ll spf[MAXN+5];vector<ll> prime; */
/* void sieve(ll n)        {forn(i,2,MAXN+1)spf[i]=i;for(ll i=2;i*i<=n;i++)if(spf[i]==i)for(ll j=i*i;j<=n;j+=i)if(spf[j]==j)spf[j]=i;forn(i,2,MAXN+1)if(spf[i]==i)prime.push_back(i);} */

//-------------------------------L_I_Erq34-------------------------------

int main()
{
	fastio();
	ll z,n,m,t,k,i,j,l,d,h,r;
	cin>>n>>m;
	vector<string> a(n);
	ll x1,y1,x2,y2;
	cin>>x1>>y1;
	x1--,y1--;
	cin>>x2>>y2;
	x2--,y2--;
	for(auto &i:a)
		cin>>i;
	vector<vector<ll>> mark(n,vector<ll>(m,inf));
	vector<vector<bool>> visited(n,vector<bool>(m));
	queue<pair<ll,ll>> q,q1;
	q.push({x1,y1});
	mark[x1][y1]=0;
	const vector<ll> dx={1,-1,0,0};
	const vector<ll> dy={0,0,1,-1};
	while(!q.empty())
	{
		auto cur=q.front();
		q.pop();
		if(visited[cur.ff][cur.ss])
		{
			if(q.empty())
				while(!q1.empty())
				{
					q.push(q1.front());
					q1.pop();
				}
			continue;
		}
		visited[cur.ff][cur.ss]=true;
		forn(r,0,4)
		{
			ll x=cur.ff+dx[r];
			ll y=cur.ss+dy[r];
			if(x>=0 and x<n and y>=0 and y<m and a[x][y]!='#' and mark[x][y]>mark[cur.ff][cur.ss])
			{
				mark[x][y]=mark[cur.ff][cur.ss];
				q.push({x,y});
			}
		}
		for(i=cur.ff-2;i<=cur.ff+2;i++)
			for(j=cur.ss-2;j<=cur.ss+2;j++)
				if(i>=0 and i<n and j>=0 and j<m and a[i][j]!='#' and mark[i][j]>mark[cur.ff][cur.ss]+1)
				{
					mark[i][j]=mark[cur.ff][cur.ss]+1;
					q1.push({i,j});
				}
		if(q.empty())
			while(!q1.empty())
			{
				q.push(q1.front());
				q1.pop();
			}
	}
	ll ans=visited[x2][y2]?mark[x2][y2]:-1;
	cout<<ans<<"\n";
	cerr<<"\nTime elapsed: "<<1000*clock()/CLOCKS_PER_SEC<<"ms\n";
	return 0;
}


Measured memory_bytes: 12840