#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define n_l '\n'

#ifndef ONLINE_JUDGE
#define dbg(...) cout << "[" << #__VA_ARGS__ << "]: "; cout << to_string(__VA_ARGS__) << endl
template <typename T, size_t N> int SIZE(const T (&t)[N]){ return N; } template<typename T> int SIZE(const T &t){ return t.size(); } string to_string(const string s, int x1=0, int x2=1e9){ return '"' + ((x1 < s.size()) ? s.substr(x1, x2-x1+1) : "") + '"'; } string to_string(const char* s) { return to_string((string) s); } string to_string(const bool b) { return (b ? "true" : "false"); } string to_string(const char c){ return string({c}); } template<size_t N> string to_string(const bitset<N> &b, int x1=0, int x2=1e9){ string t = ""; for(int __iii__ = min(x1,SIZE(b)),  __jjj__ = min(x2, SIZE(b)-1); __iii__ <= __jjj__; ++__iii__){ t += b[__iii__] + '0'; } return '"' + t + '"'; } template <typename A, typename... C> string to_string(const A (&v), int x1=0, int x2=1e9, C... coords); int l_v_l_v_l = 0, t_a_b_s = 0; template <typename A, typename B> string to_string(const pair<A, B> &p) { l_v_l_v_l++; string res = "(" + to_string(p.first) + ", " + to_string(p.second) + ")"; l_v_l_v_l--; return res; } template <typename A, typename... C> string to_string(const A (&v), int x1, int x2, C... coords) { int rnk = rank<A>::value; string tab(t_a_b_s, ' '); string res = ""; bool first = true; if(l_v_l_v_l == 0) res += n_l; res += tab + "["; x1 = min(x1, SIZE(v)), x2 = min(x2, SIZE(v)); auto l = begin(v); advance(l, x1); auto r = l; advance(r, (x2-x1) + (x2 < SIZE(v))); for (auto e = l; e != r; e = next(e)) { if (!first) { res += ", "; } first = false; l_v_l_v_l++; if(e != l){ if(rnk > 1) { res += n_l; t_a_b_s = l_v_l_v_l; }; } else{ t_a_b_s = 0; } res += to_string(*e, coords...); l_v_l_v_l--; } res += "]"; if(l_v_l_v_l == 0) res += n_l; return res; } void dbgm(){;} template<typename Heads, typename... Tails> void dbgm(Heads H, Tails... T){ cout << to_string(H) << " | "; dbgm(T...); } 
#define dbgm(...) cout << "[" << #__VA_ARGS__ << "]: "; dbgm(__VA_ARGS__); cout << endl
#endif

#define pb push_back
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define sz(x) ((int)(x).size())
#define forn(i,n) for(int i=0;i<n;i++)
#define for1(i,n) for(int i=1;i<=n;i++)
typedef vector<int> vi;
typedef vector<ll> vl;
typedef pair<int,int> pii;
typedef double db;
typedef vector<vi> vvi;
const ll mod=1000000007;
const ll N=1005; //check this
int dx[] = {-1, 0, 1, 0, 1, 1, -1, -1};
int dy[] = {0, -1, 0, 1, 1, -1, 1, -1};

ll powmod(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
ll powb(ll a,ll b) {ll res=1;a ; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a;a=a*a;}return res;}
ll gcd(ll a,ll b) { return b?gcd(b,a%b):a;}

int n,m,sx,sy,tx,ty;
char a[N][N];
int dis[N][N];
bool valid(int x,int y){
	if(x<0 || y<0 || x>=n || y>=m || a[x][y]=='#')return false;
	return true;
}

int main(){
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);

    #ifndef ONLINE_JUDGE
    freopen("inputf.in", "r", stdin);
    freopen("outputf.in", "w", stdout);
    #endif

    cin>>n>>m;
    cin>>sx>>sy;
    cin>>tx>>ty;
    sx--,sy--,tx--,ty--;
    forn(i,n)forn(j,m)cin>>a[i][j];
    forn(i,n)forn(j,m)dis[i][j]=1e8;
    deque<array<int,2>> dq;
    dq.push_front({sx,sy});
    dis[sx][sy]=0;
    while(!dq.empty()){
    	int x=(dq.front())[0],y=dq.front()[1];
    	dq.pop_front();
    	for(int d=0;d<4;d++){
    		int xx=x+dx[d],yy=y+dy[d];
    		if(!valid(xx,yy))continue;
    		if(dis[x][y]<dis[xx][yy]){
    			dis[xx][yy]=dis[x][y];
    			dq.push_front({xx,yy});
    		}
    	}
    	for(int i=x-2;i<=x+2;i++){
    		for(int j=y-2;j<=y+2;j++){
    			if(!valid(i,j))continue;
    			if(dis[i][j]>dis[x][y]+1){
    				dis[i][j]=dis[x][y]+1;
    				dq.push_back({i,j});
    			}
    		}
    	}
    }
    if(dis[tx][ty]>1e7)cout<<"-1";
    else cout<<dis[tx][ty];

}


Measured memory_bytes: 8576