#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;

class UF {
private:
  vector<int> data;
  void init(int n) {
    data.assign(n, -1);
  }

public:
  UF() {}
  UF(int n) {
    init(n);
  }
  int root(int x) {
    if (data[x] < 0) return x;
    return data[x] = root(data[x]);
  }
  bool unite(int x, int y) {
    x = root(x);
    y = root(y);
    if (x == y) return false;
    if (data[x] > data[y]) swap(x, y);
    data[x] += data[y];
    data[y] = x;
    return true;
  }
  int size(int x) {
    return -data[root(x)];
  }
  bool same(int x, int y) {
    return root(x) == root(y);
  }
  set<int> get_roots() {
    set<int> roots;
    for (size_t i = 0; i < data.size(); ++i) {
      roots.insert(root(i));
    }
    return roots;
  }
};

UF prepare_uf(int h, int w, vvi& board) {
  UF uf(h * w);
  rep (i, h) {
    rep (j, w - 1) {
      if (board[i][j] == 0 and board[i][j + 1] == 0) {
        uf.unite(i * w + j, i * w + j + 1);
      }
    }
  }
  rep (i, h - 1) {
    rep (j, w) {
      if (board[i][j] == 0 and board[i + 1][j] == 0) {
        uf.unite(i * w + j, (i + 1) * w + j);
      }
    }
  }
  return uf;
}

auto get_roots(int h, int w, vvi& board, UF& uf) {
  set<int> roots;
  rep (i, h) {
    rep (j, w) {
      if (board[i][j] == 1) {
        continue;
      }
      roots.insert(uf.root(i * w + j));
    }
  }
  return roots;
}

auto get_root_id(set<int>& roots) {
  unordered_map<int, int> root_id;
  for (auto root : roots) {
    if (root_id.find(root) == root_id.end()) {
      root_id[root] = (int)root_id.size();
    }
  }
  return root_id;
}

auto get_graph(int h, int w, vvi& board, UF& uf, unordered_map<int, int>& root_id) {
  vector<set<int> > g(root_id.size());
  rep (i, h) {
    rep (j, w) {
      if (board[i][j] == 1) {
        continue;
      }
      int num = i * w + j;
      int rid = root_id[uf.root(num)];
      FOR (di, -2, 3) {
        if (i + di < 0 or h <= i + di) {
          continue;
        }
        FOR (dj, -2, 3) {
          if (j + dj < 0 or w <= j + dj) {
            continue;
          }
          if (board[i + di][j + dj] == 1) {
            continue;
          }
          int num2 = (i + di) * w + j + dj;
          if (uf.same(num, num2)) {
            continue;
          }
          int rid2 = root_id[uf.root(num2)];
          g[rid].insert(rid2);
          g[rid2].insert(rid);
        }
      }
    }
  }
  return g;
}

int INF = 1e9;
auto dijkstra(int n, vector<set<int> >& g, int s) {
  vi d(n, INF);
  using pii=pair<int, int>;
  priority_queue<pii, vector<pii>, greater<pii> > q;
  q.push({0, s});
  d[s] = 0;
  while (!q.empty()) {
    auto d_u = q.top();
    q.pop();
    int u = d_u.second;
    if (d[u] < d_u.first) {
      continue;
    }
    for (auto v : g[u]) {
      if (d[v] > d[u] + 1) {
        d[v] = d[u] + 1;
        q.push({d[v], v});
      }
    }
  }
  return d;
}

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 uf = prepare_uf(h, w, board);
  auto roots = get_roots(h, w, board, uf);
  auto root_id = get_root_id(roots);
  debug("root_id");
  for (auto p : root_id) {
    debug2(p.first, p.second);
  }
  auto g = get_graph(h, w, board, uf, root_id);
  int start = root_id[uf.root(ch * w + cw)];
  auto d = dijkstra(root_id.size(), g, start);
  int goal = root_id[uf.root(dh * w + dw)];
  debug2(start, goal);
  int answer = d[goal];
  if (answer == INF) {
    print(-1);
  } else {
    print(answer);
  }
}

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


Measured memory_bytes: 45720