#include <algorithm>
#include <bitset>
#include <cmath>
#include <complex>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <regex>
#include <set>
#include <stack>
#include <string>
#include <vector>

const int MOD = 1e9 + 7;
const int iINF = 2147483647 / 2;
const long long int llINF = 9223372036854775807 / 2;

using namespace std;
using ll = long long int;
using vl = vector<ll>;
using vvl = vector<vector<ll>>;
using vvvl = vector<vector<vector<ll>>>;

typedef pair<ll, ll> pll;
bool paircomp(const pll &a, const pll &b) {
  if (a.first == b.first)
    return a.second < b.second;
  return a.first < b.first;
}

#define REP(i, n) for (ll i = 0; i < (n); i++)
#define RREP(i, n) for (ll i = (n)-1; i >= 0; i--)
#define FOR(i, a, b) for (ll i = (a); i < (b); i++)
#define AUTO(i, m) for (auto &i : m)
#define ALL(a) (a).begin(), (a).end()
#define MAX(vec) *std::max_element(vec.begin(), vec.end())
#define MIN(vec) *std::min_element(vec.begin(), vec.end())
#define ARGMAX(vec)                                                            \
  std::distance(vec.begin(), std::max_element(vec.begin(), vec.end()))
#define ARGMIN(vec)                                                            \
  std::distance(vec.begin(), std::min_element(vec.begin(), vec.end()))
#define REV(T) greater<T>()
#define PQ(T) priority_queue<T, vector<T>, greater<T>>
#define VVL(a, b, c) vector<vector<ll>>(a, vector<ll>(b, c))
#define VV(T, a, b, c) vector<vector<T>>(a, vector<T>(b, c))
#define VVVL(a, b, c, d)                                                       \
  vector<vector<vector<ll>>>(a, vector<vector<ll>>(b, vector<ll>(c, d)))
#define VVV(T, a, b, c, d)                                                     \
  vector<vector<vector<T>>>(a, vector<vector<T>>(b, vector<T>(c, d)))
#define SP(a) fixed << setprecision(a)
#define SQRT(a) sqrt((long double)(a))
#define DPOW(a, b) pow((long double)(a), (long double)(b))
#define UNIQUE(vec)                                                            \
  do {                                                                         \
    sort(ALL((vec)));                                                          \
    (vec).erase(std::unique(ALL((vec))), (vec).end());                         \
  } while (0)

ll POW(ll n, ll m) {
  if (m == 0) {
    return 1;
  } else if (m % 2 == 0) {
    ll tmp = POW(n, m / 2);
    return (tmp * tmp);
  } else {
    return (n * POW(n, m - 1));
  }
}

int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  ll H, W;
  cin >> H >> W;
  ll Ch, Cw, Dh, Dw;
  cin >> Ch >> Cw >> Dh >> Dw;
  Ch--;
  Cw--;
  Dh--;
  Dw--;
  vector<string> S(H);
  REP(i, H) cin >> S[i];
  vector<vector<pll>> G(H * W + 10);

  REP(h, H) REP(w, W) {
    ll now = h * W + w;
    REP(i, 4) {
      ll new_x = h + dx[i];
      ll new_y = w + dy[i];
      ll next = new_x * W + new_y;
      if (new_x >= 0 && new_x < H && new_y >= 0 && new_y < W &&
          S[new_x][new_y] == '.') {
        G[now].push_back({next, 0});
      }
    }
    REP(i1, 5) REP(i2, 5) {
      ll new_x = h + i1 - 2;
      ll new_y = w + i2 - 2;
      if (abs(new_x - h) + abs(new_y - w) <= 1)
        continue;
      ll next = new_x * W + new_y;
      if (new_x >= 0 && new_x < H && new_y >= 0 && new_y < W &&
          S[new_x][new_y] == '.') {
        G[now].push_back({next, 1});
      }
    }
  }

  // priority_queue<pll> Q;
  // PQ(tuple<ll, ll, ll>) Q;

  priority_queue<tuple<ll, ll, ll>, vector<tuple<ll, ll, ll>>,
                 greater<tuple<ll, ll, ll>>>
      Q;

  Q.push({0, 0, Ch * W + Cw});
  vl DP(H * W + 10, llINF);

  // auto q = Q.top();
  // cout << q.first << endl;
  // return 0;
  while (!Q.empty()) {
    auto q = Q.top();
    Q.pop();
    ll cost = get<0>(q);
    ll c = get<1>(q);
    ll now = get<2>(q);
    if (DP[now] <= c)
      continue;
    DP[now] = c;

    // cout << "----" << endl;
    // cout << now / W << "," << now % W << DP[now] << endl;
    AUTO(g, G[now]) {
      // cout << g.first / W << "," << g.first % W << endl;
      ll new_x = g.first / W;
      ll new_y = g.first % W;
      ll dist = abs(new_x - Dh) + abs(new_y - Dw);
      if (DP[g.first] > g.second + c + dist) {
        // cout << now << "," << DP[now] << "," << g.second + cost << endl;
        Q.push({g.second, c + g.second, g.first});
      }
    }
    // if (c >= 10)
    //  break;
    // break;
  }
  if (DP[Dh * W + Dw] == llINF)
    cout << -1 << endl;
  else
    cout << DP[Dh * W + Dw] << endl;

  return 0;
}


Measured memory_bytes: 300780