#include <bits/stdc++.h>  // This will work only for g++ compiler. 
#include <ext/pb_ds/assoc_container.hpp> // Used to include policy based data structure 
using namespace __gnu_pbds;  // Only for g++ compiler
using namespace std;

#define for0(i, n) for (int i = 0; i < (int)(n); ++i) // 0 based indexing
#define for1(i, n) for (int i = 1; i <= (int)(n); ++i) // 1 based indexing
#define forc(i, l, r) for (int i = (int)(l); i <= (int)(r); ++i) // closed interver from l to r r inclusive
#define forr0(i, n) for (int i = (int)(n) - 1; i >= 0; --i) // reverse 0 based.
#define forr1(i, n) for (int i = (int)(n); i >= 1; --i) // reverse 1 based
#define max(a, b)  (a > b) ?a :b  // max of 2 elements 
#define min(a, b)  (a < b) ?a :b  // min of 2 elements

//short hand for usual tokens
#define pb              push_back
#define fi              first
#define se              second
#define mp              make_pair
#define mii             map<int,int>
#define pqb             priority_queue<int>   // Max Heap
#define pqs             priority_queue<int,vi,greater<int> >   // Min Heap
#define setbits(x)      __builtin_popcountll(x)   // returns the number of set bits in the binary representation of x
#define zrobits(x)      __builtin_ctzll(x)   // returns the number of zeroes before the first set bit in the binary representation of x       
#define mod             1000000007   // 1e9 + 7   
#define inf             1e18   // pow(10, 18)  
#define mk(arr,n,type)  type *arr=new type[n];   // generates a dynamic array
#define w(x)            int x; cin>>x; while(x--)   // for taking test cases 
mt19937                 rng(chrono::steady_clock::now().time_since_epoch().count());   // used with shuffle

// to be used with algorithms that processes a container Eg: find(all(c),42)
#define all(x) (x).begin(), (x).end() //Forward traversal
#define rall(x) (x).rbegin, (x).rend() //reverse traversal

// traversal function to avoid long template definition. Now with C++11 auto alleviates the pain.
#define tr(c,i) for(__typeof__((c)).begin() i = (c).begin(); i != (c).end(); i++)

// find if a given value is present in a container. Container version. Runs in log(n) for set and map
#define present(c,x) ((c).find(x) != (c).end())

//find version works for all containers. This is present in std namespace.
#define cpresent(c,x) (find(all(c),x) != (c).end())

// Avoiding wrap around of size()-1 where size is a unsigned int.
#define sz(a) int((a).size())


typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> pbds;   // Used to implement policy-based data structure

// Shorthand for commonly used types
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef long long ll;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef double ld;

ll moduloMultiplication(ll a, ll b){
    ll res = 0;
    a %= mod;

    while(b){
    	if(b & 1)
    		res = (res + a)%mod;

    	a = (2*a)%mod;
    	b >>= 1;
    } 

    return res;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.precision(10);
    cout << fixed;
    
    int h, w, ch, cw, dh, dw;
    cin>>h;
    cin>>w;
    cin>>ch;
    cin>>cw;
    cin>>dh;
    cin>>dw;
    ch--;
    cw--;
    dh--;
    dw--;
    vector<string> grid(h);
    for0(i, h)
       cin>>grid[i];

    deque<int> xs, ys;
    xs.pb(ch);
    ys.pb(cw);
    vvi dist(h);
    for0(i, h)
       dist[i].assign(w, 1e7);

    dist[ch][cw] = 0;
    int dx[4] = {-1, 1, 0, 0};
    int dy[4] = {0, 0, 1, -1};
    while(!xs.empty()){
        int curX = xs.front(), curY = ys.front();
        xs.pop_front();
        ys.pop_front();
        for(int i = 0; i < 4; i++){
            int x = curX + dx[i];
            int y = curY + dy[i];
            if(x < 0 || y < 0 || x >= h || y >= w || grid[x][y] == '#')
                continue;

            if(dist[x][y] > dist[curX][curY]){
                dist[x][y] = dist[curX][curY];
                xs.push_front(x);
                ys.push_front(y);
            }
        }

        for(int i = curX-2; i <= curX+2; i++){
            for(int j = curY-2; j <= curY+2; j++){
                if(i < 0 || j < 0 || i >= h || j >= w || grid[i][j] == '#')
                  continue;

                if(dist[i][j] > dist[curX][curY]+1){
                    dist[i][j] = dist[curX][curY]+1;
                    xs.push_back(i);
                    ys.push_back(j);
                }                  
            }
        } 
    }

    if(dist[dh][dw] >= 1e7)
        cout<<-1;
    else 
        cout<<dist[dh][dw];         

    return 0;
}


Measured memory_bytes: 8604