#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx")
#pragma GCC optimize("unroll-loops")
//#pragma warning(disable : 4996)

#ifdef _MSC_VER
#include <intrin.h>
#define __builtin_popcount __popcnt
#define __builtin_popcountll __popcnt64

#endif

#include <limits.h>
#include <math.h>
#include <time.h>

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <complex>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>

using namespace std;

#define REP(i, n) for (int i = 0; i < (n); ++i)
#define REPR(i, n) for (int i = n - 1; i >= 0; --i)
#define FOR(i, m, n) for (int i = m; i < n; ++i)
#define FORR(i, m, n) for (int i = m - 1; i >= n; --i)
#define SORT(v, n) sort(v, v + n);
#define VSORT(v) sort(v.begin(), v.end());
#define REVERSE(v, n) reverse(v, v + n);
#define VREVERSE(v) reverse(v.begin(), v.end())
#define ll long long
#define print(x) cout << (x) << '\n'
#define pe(x) cout << (x) << " "
#define DEBUG(x) cout << #x << ": " << x << endl
#define lb(v, n) lower_bound(v.begin(), v.end(), (n))
#define ub(v, n) upper_bound(v.begin(), v.end(), (n))
#define int long long
//#define double long double
#define all(x) (x).begin(), (x).end()
#define print_space(v) REP(i, v.size()) cout << v[i] << " \n"[i==(int)v.size()-1]
template <typename T1, typename T2> inline void chmin(T1& a, T2 b) { if (a > b) a = b; }
template <typename T1, typename T2> inline void chmax(T1& a, T2 b) { if (a < b) a = b; }
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;
std::random_device rd;
std::mt19937 mt(rd());
constexpr ll MOD = 1e9 + 7;
constexpr int MAX = 500050;
const double pi = acos(-1);
constexpr double EPS = 1e-8;
constexpr ll LINF = 1e17 + 1;
constexpr int INF = 1e9 + 1;
int dx[4] = { 0,0,-1,1 }, dy[4] = { 1,-1,0,0 };

int H, W;
char A[1010][1010];
int d[1010][1010];
void solve() {
	cin >> H >> W;
	int sx, sy, gx, gy;
	cin >> sx >> sy >> gx >> gy;
	sx--, sy--, gx--, gy--;
	REP(i, H)REP(j, W) {
		cin >> A[i][j];
	}
	REP(i, H)REP(j, W)d[i][j] = INF;
	d[sx][sy] = 0;
	using arr3 = array<int, 3>;
	priority_queue<arr3, vector<arr3>, greater<arr3>>que;
	que.push({ 0,sx,sy });
	while (!que.empty()) {
		arr3 arr = que.top();
		que.pop();
		int res = arr[0], x = arr[1], y = arr[2];
		if (res > d[x][y])continue;
		REP(k, 4) {
			int nx = x + dx[k], ny = y+dy[k];
			if (nx >= 0 && nx < H&&ny >= 0 && ny <= W && A[nx][ny] == '.') {
				if (d[nx][ny] > d[x][y]) {
					d[nx][ny] = d[x][y];
					que.push({ d[nx][ny],nx,ny });
				}
			}
		}
		REP(i, 5) {
			REP(j, 5) {
				int nx = x + i - 2, ny = y + j - 2;
				if (nx >= 0 && nx < H&&ny >= 0 && ny <= W && A[nx][ny] == '.') {
					if (d[nx][ny] > d[x][y]+1) {
						d[nx][ny] = d[x][y]+1;
						que.push({ d[nx][ny],nx,ny });
					}
				}
			}
		}
	}
	if (d[gx][gy] < INF)print(d[gx][gy]);
	else print(-1);
}



signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	//int q;
	//cin >> q;
	//while (q--)
	solve();

}


Measured memory_bytes: 12712