// {{{ by unolight
#include <bits/stdc++.h>
#include <unistd.h>
#pragma GCC diagnostic ignored "-Wunused-result"
#pragma GCC diagnostic ignored "-Wunused-function"
#define SZ(x) ((int)(x).size())
#define ALL(x) begin(x),end(x)
#define RALL(x) rbegin(x),rend(x)
#define REP(i,n) for ( int i=0; i<int(n); i++ )
#define REP1(i,a,b) for ( int i=(a); i<=int(b); i++ )
#define MP make_pair
#define PB push_back
using namespace std;
typedef int64_t LL;
typedef pair<int,int> PII;
typedef vector<int> VI;

namespace { namespace unolight {
// Read Input
template<class T> void _R( T &x ) { cin>>x; }
void _R( int &x ) { scanf("%d",&x); }
void _R( int64_t &x ) { scanf("%" PRId64,&x); }
void _R( double &x ) { scanf("%lf",&x); }
void _R( char &x ) { scanf(" %c",&x); }
void _R( char *x ) { scanf("%s",x); }
void R() {}
template<class T, class... U> void R( T& head, U&... tail ) { _R(head); R(tail...); }
// Write Output
template<class T> void _W( const T &x ) { cout<<x; }
void _W( const int &x ) { printf("%d",x); }
void _W( const int64_t &x ) { printf("%" PRId64,x); }
void _W( const double &x ) { printf("%.16f\n",x); }
void _W( const char &x ) { putchar(x); }
void _W( const char *x ) { printf("%s",x); }
template<class T> void _W( const vector<T> &x ) { for (auto i = x.begin(); i != x.end(); _W(*i++)) if (i != x.cbegin()) putchar(' '); }
void W() {}
template<class T, class... U> void W( const T& head, const U&... tail ) { _W(head); putchar(sizeof...(tail)?' ':'\n'); W(tail...); }

#ifdef UNOLIGHT
#include "dump.hpp"
#else
#define dump(...)
#endif

template<class T> inline bool chmax( T &a, const T &b ) { return b>a ? a=b,true : false; }
template<class T> inline bool chmin( T &a, const T &b ) { return b<a ? a=b,true : false; }
template<class T> using MaxHeap = priority_queue<T>;
template<class T> using MinHeap = priority_queue<T, vector<T>, greater<T>>;
template<class T, class F=less<T>> void sort_uniq( vector<T> &v, F f=F() ) {
    sort(begin(v),end(v),f);
    v.resize(unique(begin(v),end(v))-begin(v));
}
// }}}

const int INF=1e9;
int n,m,sx,sy,tx,ty;
const int dx[4]={1,0,-1,0};
const int dy[4]={0,1,0,-1};
int f( int x, int y ) {
    return x*m+y;
}
void main() {
    R(n,m,sx,sy,tx,ty);
    --sx; --sy; --tx; --ty;
    vector<string> G(n);
    REP(i,n) cin >> G[i];
    deque<PII> q;
    VI d(n*m, INF);
    q.push_back({f(sx,sy), 0});
    d[f(sx,sy)]=0;
    while ( SZ(q) ) {
        auto p=q.front();
        int x=p.first/m;
        int y=p.first%m;
        q.pop_front();
        if ( d[p.first]!=p.second ) continue;
        // no magic
        REP(i,4) {
            int nx=x+dx[i],ny=y+dy[i];
            if ( nx>=0 && nx<n && ny>=0 && ny<m && G[nx][ny]!='#' && d[f(nx,ny)]>p.second ) {
                d[f(nx,ny)]=p.second;
                q.push_front({f(nx,ny),p.second});
            }
        }
        // magic
        for ( int i=-2; i<=2; i++ ) {
            for ( int j=-2; j<=2; j++ ) {
                int nx=x+i,ny=y+j;
                if ( nx>=0 && nx<n && ny>=0 && ny<m && G[nx][ny]!='#' && d[f(nx,ny)]>p.second+1 ) {
                    d[f(nx,ny)]=p.second+1;
                    q.push_back({f(nx,ny),p.second+1});
                }
            }
        }
    }
    if ( d[f(tx,ty)]<INF ) W(d[f(tx,ty)]);
    else W(-1);
}

}} // {{{ main
int main() { unolight::main(); return 0; }
// }}}

Measured memory_bytes: 9328