#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ordered_set tree<ll, null_type,less<ll>, rb_tree_tag,tree_order_statistics_node_update>   
using namespace std;
using namespace __gnu_pbds;
typedef long long ll; 
#define int long long
typedef unsigned long long lu;
typedef vector<ll> v;
typedef vector<vector<ll> > vv;
typedef vector<string>  vs;
typedef vector<pair<ll,ll>> vpr;
typedef vector<bool>vb;
typedef vector<double>vd;
typedef long double ld;
#define f(i,n) for(ll i = 0; i < n; i++)
#define ff(i,n) for(ll i=1;i<=n;i++)
#define pb push_back
#define mp make_pair
#define endl "\n"
#define fi first
#define se second
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define amax(x,y) if(y>x) x=y;
#define amin(x,y) if(y<x)x=y;
#define bg(x) x.begin()
#define sz(x) (ll)x.size()
#define in(x,n) for(ll i=0;i<n;i++)cin>>x[i]
#define out(x,n) for(ll i=0;i<n;i++)cout<<x[i]<<" " 
#define mxt(a) *(max_element(a.begin(),a.end()))
#define mnt(a) *(min_element(a.begin(),a.end())
#define tc ll t;cin>>t;while(t--)
typedef pair<ll,ll> pi;
#define yes cout<<"YES\n";
#define no cout<<"NO\n";
#define yesno(f) if(f) yes else no
const v dx = {1, -1, 0, 0};
const v dy = {0, 0, 1, -1};
const ld PI = 2 * acos(0.0);
ll cel(ll x1,ll y1){if((x1%y1)==0)return x1/y1;else return x1/y1+1;}
ll power(ll a,ll b,ll m)
{
    if(b==0)
        return 1;
    ll d=power(a,b/2,m);
    d=(d*d)%m;
    if(b&1)
        d=(d*a)%m;
    return d;
}
const ll mod=1e9+7;
int MOD(int a)
{
    if(a<0)
        a+=mod;
    if(a>=mod)
        a%=mod;
    return a;
}
// set_name.find_by_order(k) It returns to an iterator to the kth element (counting from zero) in the set in O(logn) time
// set_name.order_of_key(k) It returns to the number of items that are strictly smaller than our item k in O(logn) time.
/*string operations :
str.substr (x,y) : returns a substring str[x],str[x+1],...str[x+y-1]
str.substr (x) : returns a substring str[x],... end of string
str.find(qtr) : returns the first occurenece of qtr in str */
#define valid(i,j) (i>=0 && i<n && j>=0 && j<m)
void dfs(int x,int y,vector<vb> &floodfill,vs &grid,queue<pi>&que,vector<vb> &vst,vv &dist)
{
	vpr positions{{x+1,y},{x-1,y},{x,y-1},{x,y+1}};
	int n=sz(grid),m=sz(grid[0]);
	for(auto it:positions)
	{
		if(valid(it.fi,it.se) && grid[it.fi][it.se]=='.' && !floodfill[it.fi][it.se])
		{
			floodfill[it.fi][it.se]=true;
			vst[it.fi][it.se]=true;
			dist[it.fi][it.se]=dist[x][y];
			que.push({it.fi,it.se});
			dfs(it.fi,it.se,floodfill,grid,que,vst,dist);
		}
	}
}
int32_t main()
{
    ios::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
    // freopen("input.txt", "r", stdin);
    // freopen("output.txt", "w", stdout);
    int n,m;cin>>n>>m;
    int a,b,c,d;cin>>a>>b>>c>>d;
    a--;
    b--;
    c--;
    d--;
    vs grid(n);in(grid,n);
    vv dist(n,v(m,0));
    vector<vb> vst(n,vb(m,false)),floodfill(n,vb(m,false));
    vst[a][b]=true;
    queue<pi>que;
    que.push({a,b});

    while(!que.empty())
    {

    	queue<pi>que2;

    	while(!que.empty())
    	{

    		int x=que.front().fi,y=que.front().se;
    		que.pop();
    		que2.push({x,y});
    		if(floodfill[x][y])
    		{
    			continue;
    		}

    		dfs(x,y,floodfill,grid,que2,vst,dist);
    	}
    
    	while(!que2.empty())
    	{
    		int x=que2.front().fi,y=que2.front().se;
    		que2.pop();
    		for(int i=x-2;i<=x+2;i++)
    		{
    			for(int j=y-2;j<=y+2;j++)
    			{
    				if(valid(i,j) && !vst[i][j] && grid[i][j]=='.')
    				{
    					dist[i][j]=dist[x][y]+1;
    					vst[i][j]=true;
    					que.push({i,j});
    				}
    			}
    		}
    	}
    	// return 0;
    }
    if(!vst[c][d])
    {
    	cout<<-1<<endl;
    }
    else
    	cout<<dist[c][d]<<endl;
    return 0;
}

Measured memory_bytes: 13060