#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define R cin>>
#define ll long long
#define ln cout<<'\n'
#define in(a) insert(a)
#define pb(a) push_back(a)
#define pd(a) printf("%.10f\n",a)
#define mem(a) memset(a,0,sizeof(a))
#define all(c) (c).begin(),(c).end()
#define iter(c) __typeof((c).begin())
#define rrep(i,n) for(ll i=(ll)(n)-1;i>=0;i--)
#define REP(i,m,n) for(ll i=(ll)(m);i<(ll)(n);i++)
#define rep(i,n) REP(i,0,n)
#define tr(it,c) for(iter(c) it=(c).begin();it!=(c).end();it++)
ll check(ll n,ll m,ll x,ll y){return x>=0&&x<n&&y>=0&&y<m;}void pr(){ln;}
template<class A,class...B>void pr(const A &a,const B&...b){cout<<a<<(sizeof...(b)?" ":"");pr(b...);}
template<class A>void PR(A a,ll n){rep(i,n)cout<<(i?" ":"")<<a[i];ln;}
const ll MAX=1e9+7,MAXL=1LL<<61,dx[8]={-1,0,1,0,-1,-1,1,1},dy[8]={0,1,0,-1,-1,1,1,-1};
typedef pair<ll,ll> P;

ll n,m;
string s[2222];
vector<vector<ll> > bfs(int sx,int sy) {
  vector<vector<ll> > d(n,vector<ll>(m,MAX));
  d[sx][sy]=0;
  queue<P> que;
  que.push(P(sx,sy));
  while(!que.empty()) {
    P p=que.front();que.pop();
    ll x=p.F,y=p.S;
    rep(i,4) {
      ll xx=x+dx[i],yy=y+dy[i];
      if(check(n,m,xx,yy)&&s[xx][yy]=='.'&&d[xx][yy]==MAX) {
        d[xx][yy]=d[x][y]+1;
        que.push(P(xx,yy));
      }
    }
  }
  return d;
}

void Main() {
  ll sx,sy,tx,ty;
  cin >> n >> m >> sx >> sy >> tx >> ty;
  rep(i,n) cin >> s[i];
  sx--,sy--,tx--,ty--;
  vector<vector<ll> > c=bfs(sx,sy);
  vector<vector<ll> > d=bfs(tx,ty);
  ll ans=MAX;
  vector<P> v;
  rep(i,n) {
    rep(j,m) {
      if(s[i][j]=='.') {
        ll dd=c[i][j]+d[i][j];
        if(dd==c[tx][ty]) v.pb(P(i,j));
      }
    }
  }
  if(v.size()>c[tx][ty]+1) {
    pr(c[tx][ty]*2);
    return;
  }
  rep(i,n) {
    rep(j,m) {
      ll dd=c[i][j]+d[i][j];
      if(dd==c[tx][ty]) {
        vector<P> v;
        rep(k,4) {
          int x=i+dx[k],y=j+dy[k];
          if(check(n,m,x,y)&&s[x][y]=='.') {
            ll cc=c[x][y]+d[x][y];
            if(cc!=dd) v.pb(P(x,y));
          }
        }
        if(P(i,j)!=P(sx,sy)&&P(i,j)!=P(tx,ty)) {
          if(v.size()) ans=min(ans,dd*2+2);
        } else {
          if(v.size()>=2) ans=min(ans,dd*2+4);
        }
      }
      if(c[i][j]==d[sx][sy]+d[i][j]||d[i][j]==c[tx][ty]+c[i][j]) {
        vector<P> v;
        rep(k,4) {
          int x=i+dx[k],y=j+dy[k];
          if(check(n,m,x,y)&&s[x][y]=='.') {
            ll cc=c[x][y]+d[x][y];
            if(cc!=dd) v.pb(P(x,y));
          }
        }
        if(v.size()>=2) ans=min(ans,dd*2+4);
      }
    }
  }
  if(ans==MAX) {
    s[sx][sy]='#';
    rep(k,4) {
      ll x=sx+dx[k],y=sy+dy[k];
      if(check(n,m,x,y)&&s[x][y]=='.'&&d[x][y]+c[x][y]!=c[tx][ty]) {
        vector<vector<ll> > e=bfs(x,y);
        ll dd=d[sx][sy]+e[tx][ty]+1;
        ans=min(ans,dd);
      }
    }
  }
  if(ans==MAX) ans=-1;
  pr(ans);
}

int main(){ios::sync_with_stdio(0);cin.tie(0);Main();return 0;}