/*!enjoy karo yaar!*/

//CF,CC,AtC,SPOJ: hp1999
//HE: hemant269
//HR: hemant2132

#include<bits/stdc++.h>
using namespace std;

/*-----<Defines>-----*/
#define     int             long long int
#define     fast()          ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define     all(x)          begin(x),end(x)
#define     rz(x)           resize(x)
#define     asn(x,y)        assign(x,y)
#define     mem(a,b)        memset(a,b,sizeof(a))
#define     sz(x)           ((int)size(x))
#define     eb              emplace_back
#define     pb              push_back
#define     pf              push_front
#define     pob             pop_back
#define     pof             pop_front
#define     ins             insert
#define     vi              vector<int>
#define     pii             pair<int,int>
#define     mii             map<int,int>
#define     F               first
#define     S               second
#define     remax(a,b)      a=max(a,b)
#define     remin(a,b)      a=min(a,b)
#define     bitcount(x)     __builtin_popcountll(x)
#define     iceil(n,x)      (((n)-1)/(x)+1)
#define     flush           fflush(stdout)

using ull=unsigned long long;
using ll=long long;
using ld=long double;
/*-----</Defines>-----*/

/*-----<Debugging Stuff>-----*/
string to_string(char s)
{   string res="'''";res[1]=s;return res; }

string to_string(string s)
{   return '"'+s+'"'; }

string to_string(const char* s)
{   return to_string((string)s); }

string to_string(bool b)
{   return (b?"true":"false"); }

template<typename A, typename B>
string to_string(pair<A, B> p)
{   return "("+to_string(p.F)+", "+to_string(p.S)+")"; }

template<typename A>
string to_string(A v)
{
    bool first=1; string res="{";
    for(const auto &x:v)
    {
        if(!first)  res+=", ";
        first=0;
        res+=to_string(x);
    }
    res+="}";
    return res;
}

void debug() { cout<<"\n"; }
template<typename Head, typename... Tail>
void debug(Head H, Tail... T)
{
    cout<<" "<<to_string(H);
    debug(T...);
}

#define show(...) cout << "[" << #__VA_ARGS__ << "]:", debug(__VA_ARGS__)
/*-----</Debugging Stuff>-----*/

/*-----<Mod Operations>-----*/
const int M=1e9+7;
inline int add(int a,int b,int p=M){ a=a+b; if(a>=p) a-=p; return a; }
inline int sub(int a,int b,int p=M){ a=a-b; if(a<0) a+=p; return a; }
inline int mul(int a,int b,int p=M){ a=(a*1ll*b)%p; return a; }
/*-----</Mod Operations>-----*/

/*-----<Constants>-----*/
const ld pi=acos(-1),eps=1e-9;
const ll inf=1e18;
const int N=1;
/*-----</Constants>-----*/

void solve()
{
    int n,m;
    cin>>n>>m;

    int ax,ay;
    cin>>ax>>ay;
    --ax,--ay;

    int bx,by;
    cin>>bx>>by;
    --bx,--by;

    vector<string> mat(n);
    for(auto& c:mat)
        cin>>c;

    priority_queue<pair<int,pii>> pq;
    pq.push({0,{ax,ay}});

    vector<vi> dist(n,vi(m,inf));
    vector<vi> vis(n,vi(m,0));
    dist[ax][ay]=0;

    int dx[]={-1,1,0,0};
    int dy[]={0,0,-1,1};

    auto valid=[&](int x,int y)
    {
        return (x>=0 && x<n && y>=0 && y<m && mat[x][y]=='.' && !vis[x][y]);
    };

    while(!pq.empty())
    {
        auto [val,p]=pq.top();
        pq.pop();

        auto [x,y]=p;

        vis[x][y]=1;

        for(int i=0;i<4;++i)
        {
            int a=x+dx[i];
            int b=y+dy[i];

            if(valid(a,b) && dist[a][b]>dist[x][y])
            {
                dist[a][b]=dist[x][y];
                pq.push({-dist[a][b],{a,b}});
            }
        }

        for(int i=-2;i<=2;++i)
        {
            for(int j=-2;j<=2;++j)
            {
                int a=x+i;
                int b=y+j;

                if(valid(a,b) && dist[a][b]>dist[x][y]+1)
                {
                    dist[a][b]=dist[x][y]+1;
                    pq.push({-dist[a][b],{a,b}});
                }
            }
        }
    }

    if(dist[bx][by]==inf)
        cout<<-1;
    else
        cout<<dist[bx][by];
}

int32_t main()
{
    fast();

    int t=1;
    //cin>>t;
    for(int z=1;z<=t;++z)
    {
        solve();
        //cout<<"\n";
    }

    return 0;
}




Measured memory_bytes: 20612