#include <algorithm>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <deque>
#include <iostream>
#include <iterator>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

#define FOR(i,k,n) for(int(i)=(k);(i)<(n);++(i))
#define rep(i,n) FOR(i,0,n)
#define all(v) begin(v),end(v)
#ifdef ONLINE_JUDGE
  #define debug(x)
  #define debug2(x,y)
  #define debug3(x,y,z)
  #define assert(e) if(!(e)){stod("");}
#else
  #define debug(x) std::cerr<<#x<<": "<<x<<"\n"
  #define debug2(x,y) std::cerr<<#x<<": "<<x<<", "<<#y<<": "<<y<<"\n"
  #define debug3(x,y,z) std::cerr<<#x<<": "<<x<<", "<<#y<<": "<<y<<", "<<#z<<": "<<z<<"\n"
#endif

using ll=long long;
using vi=std::vector<int>;
using vvi=std::vector<vi>;
using vll=std::vector<ll>;
using vvll=std::vector<vll>;
template<typename T> using vvec=std::vector<std::vector<T>>;
template<typename T>
auto make_v(size_t sz){return std::vector<T>(sz);}
template<typename T,typename... Ts>
auto make_v(size_t sz,Ts...ts){return std::vector<decltype(make_v<T>(ts...))>(sz,make_v<T>(ts...));}
template<typename T>
void fill_v(T&var,const T&x){var=x;}
template<typename V,typename T>
void fill_v(V&v,const T&x){for(auto&& w:v){fill_v(w,x);}}

template<typename T> std::ostream& operator<<(std::ostream&s,const std::vector<T>&v){
  int sz=v.size();s<<"\n";rep(i,sz){s<<v[i];if(i<sz-1){s<<"\t";}}s<<"\n";return s;}
template<typename T> std::ostream& operator<<(std::ostream&s,const std::vector<std::vector<T>>&v){
  for(auto&& w:v){s<<w;}return s;}
template<typename T> std::ostream& operator<<(std::ostream&s,const std::deque<T>&v){
  int sz=v.size();s<<"\n";rep(i,sz){s<<v[i];if(i<sz-1){s<<"\t";}}s<<"\n";return s;}
template<typename T> std::ostream& operator<<(std::ostream&s,const std::deque<std::deque<T>>&v){
  for(auto&& w:v){s<<w;}return s;}
template<typename T> std::ostream& operator<<(std::ostream&s, const std::set<T>&v){
  s<<"\n";for(auto&& elm:v){s<<elm<<"\t";}s<<"\n";return s;}

inline void scan(int&a){scanf("%d",&a);}
inline void scan(ll&a){scanf("%lld",&a);}
inline void scan(char&a){scanf(" %c",&a);}
inline void scan(double&a){scanf("%lf",&a);}
template<typename T>
inline void scan(std::vector<T>&v){for(auto&& sv:v){scan(sv);}}
template<typename First,typename...Args>
inline void scan(First&f,Args&...args){scan(f);scan(args...);}
inline void scan(std::string&s){char BUF[3000000];scanf(" %s",BUF);s=std::string(BUF);}
inline void print(int a){printf("%d\n",a);}
inline void print(ll a){printf("%lld\n",a);}
inline void print(double a){printf("%.12f\n",a);}
inline void print(std::string s){std::cout<<s<<"\n";}

using namespace std;

int INF = 1e9;
auto zobfs(int h, int w, int bh, int bw, vvi& board) {
  vvi distance(h, vi(w, INF));
  distance[bh][bw] = 0;
  deque<vi> dq;
  dq.push_front({bh, bw});
  while (not dq.empty()) {
    auto h_w = dq.front();
    dq.pop_front();
    int ch = h_w[0];
    int cw = h_w[1];
    vi dhv = {0, 1, 0, -1};
    vi dwv = {1, 0, -1, 0};
    rep (k, 4) {
      int nh = ch + dhv[k];
      int nw = cw + dwv[k];
      if (nh < 0 or h <= nh or nw < 0 or w <= nw) {
        continue;
      }
      if (board[nh][nw] == 1) {
        continue;
      }
      if (distance[nh][nw] > distance[ch][cw]) {
        distance[nh][nw] = distance[ch][cw];
        dq.push_front({nh, nw});
      }
    }
    FOR (dh, -2, 3) {
      FOR (dw, -2, 3) {
        int nh = ch + dh;
        int nw = cw + dw;
        if (nh < 0 or h <= nh or nw < 0 or w <= nw) {
          continue;
        }
        if (board[nh][nw] == 1) {
          continue;
        }
        if (distance[nh][nw] > distance[ch][cw] + 1) {
          distance[nh][nw] = distance[ch][cw] + 1;
          dq.push_back({nh, nw});
        }
      }
    }
  }
  return distance;
}

void solve() {
  int h, w;
  scan(h, w);
  int ch, cw;
  scan(ch, cw);
  --ch; --cw;
  int dh, dw;
  scan(dh, dw);
  --dh; --dw;
  vvi board(h, vi(w, 0));
  rep (i, h) {
    char c;
    rep (j, w) {
      scan(c);
      if (c == '#') {
        board[i][j] = 1;
      }
    }
  }
  auto distance = zobfs(h, w, ch, cw, board);
  debug(distance);
  int answer = distance[dh][dw];
  if (answer == INF) {
    print(-1);
  } else {
    print(answer);
  }
}

int main() {
  solve();
  return 0;
}


Measured memory_bytes: 11756