#include<bits/stdc++.h>

using namespace std;
 
/// ----------------------------- (Debug) ------------------------------
#define sim template < class c
#define ris return * this
#define dor > debug & operator <<
#define eni(x) sim > typename enable_if<sizeof dud<c>(0) x 1, debug&>::type operator<<(c i) {
sim > struct rge { c b, e; }; sim > rge<c> range(c i, c j) { return rge<c>{i, j}; }
sim > auto dud(c* x) -> decltype(cerr << *x, 0); sim > char dud(...);
struct debug {
#ifndef ONLINE_JUDGE
eni(!=) cerr << boolalpha << i; ris; }
eni(==) ris << range(begin(i), end(i));}
sim, class b dor(pair < b, c > d) {ris << "(" << d.first << ", " << d.second << ")";}
sim dor(rge<c> d) {*this << "["; for (auto it = d.b; it != d.e; ++it) *this << ", " + 2 * (it == d.b) << *it; ris << "]";}
#else
sim dor(const c&) { ris; }
#endif
};
vector<char*> tokenizer(const char* args) {
  char *token = new char[111]; strcpy(token, args); token = strtok(token, ", ");
  vector<char*> v({token});
  while(token = strtok(NULL,", ")) v.push_back(token);
  return reverse(v.begin(), v.end()), v;
}
void debugg(vector<char*> args) { cerr << "\b\b "; }
template <typename Head, typename... Tail>
void debugg(vector<char*> args, Head H, Tail... T) {
  debug() << " [" << args.back() << ": " << H << "] ";
  args.pop_back(); debugg(args, T...);
}
#define harg(...) #__VA_ARGS__
#ifndef ONLINE_JUDGE
#define dbg(...) { debugg(tokenizer(harg(__VA_ARGS__, \b\t-->Line)), __VA_ARGS__, __LINE__); cerr << endl;}
#else
#define dbg(...) { }
#endif
/// -----------------------------------------------------------------------

typedef long long ll;
typedef vector<int> vi;
typedef pair<int,int> pi;
typedef vector<pi> vpi; 
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0)    
#define F first
#define S second
#define PB push_back
#define EB emplace_back
#define MP make_pair
#define REP(i,a,b) for(i=a;i<=b;i++)
#define RAP(i,a,b) for(i=a;i>=b;i--)
#define spa <<" "<<
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)x.size()
ll mod=1e9+7;
const int MX=0x3f3f3f3f;
int dx[]={0,0,1,-1},dy[]={1,-1,0,0};
int mdx[]={1,1,-1,-1,2,-2,2,2,-2,-2,0,0,-1,-1,1,1,-2,-2,2,2};
int mdy[]={1,-1,1,-1,0,0,2,-2,-2,2,2,-2,2,-2,2,-2,1,-1,1,-1};
int main(){
    IOS;
    int h,w,ch,cw,dh,dw,i,j,nx,ny;
    cin>>h>>w>>ch>>cw>>dh>>dw;
    char arr[h+1][w+1];
    REP(i,1,h)
        REP(j,1,w) cin>>arr[i][j];
    int dis[h+1][w+1];
    memset(dis,MX,sizeof(dis));
    dis[ch][cw]=0;
    priority_queue<pair<int,pi>> q;
    q.push({0,{ch,cw}});
    pair<int,pi> temp;
    while(!q.empty()){
        temp=q.top();
        // dbg(temp);
        q.pop();
        if(temp.S.F==dh&&temp.S.S==dw) break;
        if(dis[temp.S.F][temp.S.S]!=-temp.F) continue;
        REP(i,0,3){
            nx=temp.S.F+dx[i];
            ny=temp.S.S+dy[i];
            // dbg(nx,ny);
            if(nx>=1&&nx<=h&&ny>=1&&ny<=w&&dis[nx][ny]>dis[temp.S.F][temp.S.S]&&arr[nx][ny]=='.'){
                dis[nx][ny]=dis[temp.S.F][temp.S.S];
                q.push({-dis[nx][ny],{nx,ny}});
            }
        }
        REP(i,0,19){
            nx=temp.S.F+mdx[i];
            ny=temp.S.S+mdy[i];
            // dbg(nx,ny);
            if(nx>=1&&nx<=h&&ny>=1&&ny<=w&&dis[nx][ny]>dis[temp.S.F][temp.S.S]+1&&arr[nx][ny]=='.'){
                dis[nx][ny]=dis[temp.S.F][temp.S.S]+1;
                q.push({-dis[nx][ny],{nx,ny}});
            }
        }
    }
    if(dis[dh][dw]==MX) cout<<-1;
    else cout<<(dis[dh][dw]);
    return 0;
}

Measured memory_bytes: 8540