#include <bits/stdc++.h>
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define rep(i,n) for (int i=0;i<(int)(n);i++)
#define codefor int test;scanf("%d",&test);while(test--)
#define INT(...) int __VA_ARGS__;in(__VA_ARGS__)
#define LL(...) ll __VA_ARGS__;in(__VA_ARGS__)
#define yn(ans) if(ans)printf("Yes\n");else printf("No\n")
#define YN(ans) if(ans)printf("YES\n");else printf("NO\n")
#define vector1d(type,name,...) vector<type>name(__VA_ARGS__)
#define vector2d(type,name,h,...) vector<vector<type>>name(h,vector<type>(__VA_ARGS__))
#define umap unordered_map
#define uset unordered_set
using namespace std;
using ll = long long;
const int MOD=1000000007;
//入力系
void scan(int& a){scanf("%d",&a);}
void scan(long long& a){scanf("%lld",&a);}
template<class T> void scan(T& a){cin>>a;}
template<class T> void scan(vector<T>& vec){for(auto&& it:vec)scan(it);}
void in(){}
template <class Head, class... Tail> void in(Head& head, Tail&... tail){scan(head);in(tail...);}
//出力系
void print(const int& a){printf("%d",a);}
void print(const long long& a){printf("%lld",a);}
void print(const double& a){printf("%.15lf",a);}
template<class T> void print(const T& a){cout<<a;}
template<class T> void print(const vector<T>& vec){if(vec.empty())return;print(vec[0]);for(auto it=vec.begin();++it!= vec.end();){putchar(' ');print(*it);}}
void out(){putchar('\n');}
template<class T> void out(const T& t){print(t);putchar('\n');}
template <class Head, class... Tail> void out(const Head& head,const Tail&... tail){print(head);putchar(' ');out(tail...);}
//デバッグ系
template<class T> void dprint(const T& a){cerr<<a;}
template<class T> void dprint(const vector<T>& vec){if(vec.empty())return;cerr<<vec[0];for(auto it=vec.begin();++it!= vec.end();){cerr<<" "<<*it;}}
void debug(){cerr<<endl;}
template<class T> void debug(const T& t){dprint(t);cerr<<endl;}
template <class Head, class... Tail> void debug(const Head& head, const Tail&... tail){dprint(head);cerr<<" ";debug(tail...);}

int main(){
    int INF=1000000000;
    pair<int,int> start,goal;
    INT(h,w,my,mx,gy,gx);
    my--;
    mx--;
    gy--;
    gx--;
    start=make_pair(my,mx);
    vector2d(char,maze,h,w);
    in(maze);
    deque<pair<int,int>> next;
    next.push_back(start);
    vector<vector<int>> checked(h,vector<int>(w,INF));
    vector2d(bool,stock,h,w,false);
    int x,y;
    checked[start.first][start.second]=0;
    stock[start.first][start.second]=true;
    while(!next.empty()){
        y=next.front().first;
        x=next.front().second;
        next.pop_front();
        if(x-1>=0&&checked[y][x]<checked[y][x-1]&&maze[y][x-1]!='#'){
            next.push_front(make_pair(y,x-1));
            checked[y][x-1]=checked[y][x];
            stock[y][x-1]=true;
        }
        if(y-1>=0&&checked[y][x]<checked[y-1][x]&&maze[y-1][x]!='#'){
            next.push_front(make_pair(y-1,x));
            checked[y-1][x]=checked[y][x];
            stock[y-1][x]=true;
        }
        if(x+1<w&&checked[y][x]<checked[y][x+1]&&maze[y][x+1]!='#'){
            next.push_front(make_pair(y,x+1));
            checked[y][x+1]=checked[y][x];
            stock[y][x+1]=true;
        }
        if(y+1<h&&checked[y][x]<checked[y+1][x]&&maze[y+1][x]!='#'){
            next.push_front(make_pair(y+1,x));
            checked[y+1][x]=checked[y][x];
            stock[y+1][x]=true;
        }
        for(int dy=-2;dy<=2;dy++){
            for(int dx=-2;dx<=2;dx++){
                if(x+dx<0||y+dy<0||x+dx>=w||y+dy>=h)continue;
                else if(checked[y][x]+1<checked[y+dy][x+dx]&&maze[y+dy][x+dx]!='#'){
                    if(!stock[y+dy][x+dx])next.push_back(make_pair(y+dy,x+dx));
                    checked[y+dy][x+dx]=checked[y][x]+1;
                }
            }
        }
    }
    //rep(i,h)out(checked[i]);
    if(checked[gy][gx]==INF)out(-1);
    else out(checked[gy][gx]);
}

Measured memory_bytes: 8956