#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define ll long long
#define pb(a) push_back(a)
#define rep(i,n) for(ll i=0;i<(ll)(n);i++)
ll check(ll n,ll m,ll x,ll y){return x>=0&&x<n&&y>=0&&y<m;}
const ll MAX=1e9+7,dx[4]={-1,0,1,0},dy[4]={0,1,0,-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 xx=p.F,yy=p.S;
    rep(i,4) {
      ll x=xx+dx[i],y=yy+dy[i];
      if(check(n,m,x,y)&&s[x][y]=='.'&&d[x][y]==MAX) {
        d[x][y]=d[xx][yy]+1;
        que.push(P(x,y));
      }
    }
  }
  return d;
}

int 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]=='.'&&c[i][j]+d[i][j]==c[tx][ty]) v.pb(P(i,j));
  if(v.size()>c[tx][ty]+1) {
    cout<<c[tx][ty]*2<<endl;
    return 0;
  }
  rep(i,n)rep(j,m) {
    if(s[i][j]=='#') continue;
    ll dd=c[i][j]+d[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]=='.') v.pb(P(x,y));
    }
    if(v.size()>=3) ans=min(ans,dd*2+(dd==c[tx][ty]&&P(i,j)!=P(sx,sy)&&P(i,j)!=P(tx,ty)?2:4));
  }
  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);
      ans=min(ans,d[sx][sy]+e[tx][ty]+1);
    }
  }
  if(ans==MAX) ans=-1;
  cout<<ans<<endl;
  return 0;
}