#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cctype>
#include <chrono>
#include <cmath>
#include <complex>
#include <cstdint>
#include <cstdlib>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <type_traits>
#include <unordered_map>
#include <utility>
#include <vector>

/* template start */

using i64 = std::int_fast64_t;
using u64 = std::uint_fast64_t;

#define rep(i, a, b) for (i64 i = (a); (i) < (b); (i)++)
#define all(i) i.begin(), i.end()

#ifdef LOCAL
#define debug(...)                                                    \
  std::cerr << "LINE: " << __LINE__ << "  [" << #__VA_ARGS__ << "]:", \
      debug_out(__VA_ARGS__)
#else
#define debug(...)
#endif

void debug_out() { std::cerr << std::endl; }

template <typename Head, typename... Tail>
void debug_out(Head h, Tail... t) {
  std::cerr << " " << h;
  if (sizeof...(t) > 0) std::cout << " :";
  debug_out(t...);
}

template <typename T1, typename T2>
std::ostream& operator<<(std::ostream& os, std::pair<T1, T2> pa) {
  return os << pa.first << " " << pa.second;
}

template <typename T>
std::ostream& operator<<(std::ostream& os, std::vector<T> vec) {
  for (std::size_t i = 0; i < vec.size(); i++)
    os << vec[i] << (i + 1 == vec.size() ? "" : " ");
  return os;
}

template <typename T1, typename T2>
inline bool chmax(T1& a, T2 b) {
  return a < b && (a = b, true);
}

template <typename T1, typename T2>
inline bool chmin(T1& a, T2 b) {
  return a > b && (a = b, true);
}

template <typename Num>
constexpr Num mypow(Num a, u64 b, Num id = 1) {
  if (b == 0) return id;
  Num x = id;
  while (b > 0) {
    if (b & 1) x *= a;
    a *= a;
    b >>= 1;
  }
  return x;
}

/* template end */

template <class T>
[[nodiscard]] inline bool in_range(const T& min, const T& val, const T& max) {
  return (min <= val) && (val < max);
}

i64 dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};

int main() {
  std::cin.tie(nullptr);
  std::ios::sync_with_stdio(false);

  i64 h, w;
  std::cin >> h >> w;

  i64 ch, cw;
  std::cin >> ch >> cw;
  ch--;
  cw--;

  i64 dh, dw;
  std::cin >> dh >> dw;
  dh--;
  dw--;

  std::vector<std::string> grid(h);
  for (auto&& e : grid) std::cin >> e;

  constexpr i64 INF = 1e18;

  std::vector<std::vector<i64>> d(h, std::vector<i64>(w, INF));

  using P = std::pair<i64, i64>;
  std::deque<P> que;

  d[ch][cw] = 0;
  que.emplace_back(ch, cw);

  while (!que.empty()) {
    auto [nh, nw] = que.front();
    que.pop_front();

    rep(i, 0, 4) {
      i64 x = nh + dx[i], y = nw + dy[i];
      if (in_range(0l, x, h) && in_range(0l, y, w) && grid[x][y] == '.' &&
          chmin(d[x][y], d[nh][nw]))
        que.emplace_front(x, y);
    }

    rep(i, -2, 3) {
      rep(j, -2, 3) {
        i64 x = nh + i, y = nw + j;
        if (in_range(0l, x, h) && in_range(0l, y, w) && grid[x][y] == '.' &&
            chmin(d[x][y], d[nh][nw]+1))
          que.emplace_back(x, y);
      }
    }
  }

  if(d[dh][dw]!=INF)std::cout<<d[dh][dw]<<"\n";
  else std::cout<<-1<<"\n";

  return 0;
}


Measured memory_bytes: 12684