#include <bits/stdc++.h>
using namespace std;
using LL = long long int;
#define incII(i, l, r) for(LL i = (l)    ; i <= (r); i++)
#define incIX(i, l, r) for(LL i = (l)    ; i <  (r); i++)
#define incXI(i, l, r) for(LL i = (l) + 1; i <= (r); i++)
#define incXX(i, l, r) for(LL i = (l) + 1; i <  (r); i++)
#define decII(i, l, r) for(LL i = (r)    ; i >= (l); i--)
#define decIX(i, l, r) for(LL i = (r) - 1; i >= (l); i--)
#define decXI(i, l, r) for(LL i = (r)    ; i >  (l); i--)
#define decXX(i, l, r) for(LL i = (r) - 1; i >  (l); i--)
#define inc(i, n)  incIX(i, 0, n)
#define dec(i, n)  decIX(i, 0, n)
#define inc1(i, n) incII(i, 1, n)
#define dec1(i, n) decII(i, 1, n)
auto inII = [](auto x, auto l, auto r) { return (l <= x && x <= r); };
auto inIX = [](auto x, auto l, auto r) { return (l <= x && x <  r); };
auto inXI = [](auto x, auto l, auto r) { return (l <  x && x <= r); };
auto inXX = [](auto x, auto l, auto r) { return (l <  x && x <  r); };
auto setmin   = [](auto & a, auto b) { return (b <  a ? a = b, true : false); };
auto setmax   = [](auto & a, auto b) { return (b >  a ? a = b, true : false); };
auto setmineq = [](auto & a, auto b) { return (b <= a ? a = b, true : false); };
auto setmaxeq = [](auto & a, auto b) { return (b >= a ? a = b, true : false); };
#define PB push_back
#define EB emplace_back
#define MP make_pair
#define MT make_tuple
#define FI first
#define SE second
#define FR front()
#define BA back()
#define ALL(c) c.begin(), c.end()
#define RALL(c) c.rbegin(), c.rend()
#define RV(c) reverse(ALL(c))
#define SC static_cast
#define SI(c) SC<int>(c.size())
#define SL(c) SC<LL >(c.size())
#define RF(e, c) for(auto & e: c)
#define SF(c, ...) for(auto & [__VA_ARGS__]: c)
#define until(e) while(! (e))
#define if_not(e) if(! (e))
#define ef else if
#define UR assert(false)
auto * IS = & cin;
auto * OS = & cout;
array<string, 3> SEQ = { "", " ", "" };
// input
template<typename T> T in() { T a; (* IS) >> a; return a; }
// input: tuple
template<int I, typename U> void tin_(istream & is, U & t) {
	if constexpr(I < tuple_size<U>::value) { is >> get<I>(t); tin_<I + 1>(is, t); }
}
template<typename ... T> istream & operator>>(istream & is, tuple<T ...> & t) { tin_<0>(is, t); return is; }
template<typename ... T> auto tin() { return in<tuple<T ...>>(); }
// input: array
template<typename T, size_t N> istream & operator>>(istream & is, array<T, N> & a) { RF(e, a) { is >> e; } return is; }
template<typename T, size_t N> auto ain() { return in<array<T, N>>(); }
// input: multi-dimensional vector
template<typename T> T vin() { T v; (* IS) >> v; return v; }
template<typename T, typename N, typename ... M> auto vin(N n, M ... m) {
	vector<decltype(vin<T, M ...>(m ...))> v(n); inc(i, n) { v[i] = vin<T, M ...>(m ...); } return v;
}
// input: multi-column (tuple<vector>)
template<typename U, int I> void colin_([[maybe_unused]] U & t) { }
template<typename U, int I, typename A, typename ... B> void colin_(U & t) {
	get<I>(t).PB(in<A>()); colin_<U, I + 1, B ...>(t);
}
template<typename ... T> auto colin(int n) {
	tuple<vector<T> ...> t; inc(i, n) { colin_<tuple<vector<T> ...>, 0, T ...>(t); } return t;
}
// output
void out_([[maybe_unused]] string s) { }
template<typename A> void out_([[maybe_unused]] string s, A && a) { (* OS) << a; }
template<typename A, typename ... B> void out_(string s, A && a, B && ... b) { (* OS) << a << s; out_(s, b ...); }
auto outF = [](auto x, auto y, auto z, auto ... a) { (* OS) << x; out_(y, a ...); (* OS) << z << flush; };
auto out  = [](auto ... a) { outF("", " " , "\n", a ...); };
auto outS = [](auto ... a) { outF("", " " , " " , a ...); };
auto outL = [](auto ... a) { outF("", "\n", "\n", a ...); };
auto outN = [](auto ... a) { outF("", ""  , ""  , a ...); };
// output: multi-dimensional vector
template<typename T> ostream & operator<<(ostream & os, vector<T> const & v) {
	os << SEQ[0]; inc(i, SI(v)) { os << (i == 0 ? "" : SEQ[1]) << v[i]; } return (os << SEQ[2]);
}
template<typename T> void vout_(T && v) { (* OS) << v; }
template<typename T, typename A, typename ... B> void vout_(T && v, A a, B ... b) {
	inc(i, SI(v)) { (* OS) << (i == 0 ? "" : a); vout_(v[i], b ...); }
}
template<typename T, typename A, typename ... B> void vout (T && v, A a, B ... b) { vout_(v, a, b ...); (* OS) << a << flush; }
template<typename T, typename A, typename ... B> void voutN(T && v, A a, B ... b) { vout_(v, a, b ...); (* OS)      << flush; }

// ---- ----

auto dd = [](int h, int w, int i, int j, int k) -> tuple<bool, int, int> {
	vector<int> di = { +1,  0, -1,  0, +1, +1, -1, -1, 0 };
	vector<int> dj = {  0, +1,  0, -1, +1, -1, +1, -1, 0 };
	int ii = i + di.at(k);
	int jj = j + dj.at(k);
	return { inIX(ii, 0, h) && inIX(jj, 0, w), ii, jj };
};

// make vector
template<typename T> T MV(T v) { return v; }
template<typename T, typename ... U> auto MV(T v, int a, U ... b) { return vector<decltype(MV(v, b ...))>(a, MV(v, b ...)); }

int main() {
	auto [h, w, ai, aj, bi, bj] = ain<int, 6>();
	ai--; aj--; bi--; bj--;
	auto s = vin<string>(h);
	
	auto dist = [&](int si, int sj, auto & D) {
		queue<array<int, 3>> q;
		auto add = [&](int i, int j, int d) {
			if(setmin(D[i][j], d)) { q.push({ i, j, d }); }
		};
		add(si, sj, 0);
		until(q.empty()) {
			auto [i, j, d] = q.front(); q.pop();
			inc(k, 4) {
				auto [f, ii, jj] = dd(h, w, i, j, k);
				if(f && s[ii][jj] == '.') { add(ii, jj, d + 1); }
			}
		}
	};
	const int INF = 1e9;
	auto da = MV<int>(INF, h, w);
	auto db = MV<int>(INF, h, w);
	auto dc = MV<int>(INF, h, w);
	dist(ai, aj, da);
	dist(bi, bj, db); s[ai][aj] = '#';
	dist(bi, bj, dc); s[ai][aj] = '.';
	if(da[bi][bj] == INF) { out(-1); exit(0); }
	
	int ans = INF;
	inc(i, h) {
	inc(j, w) {
		if(da[i][j] == INF) { continue; }
		vector<int> d;
		inc(k, 4) {
			auto [f, ii, jj] = dd(h, w, i, j, k);
			if(f && s[ii][jj] == '.') { d.PB(da[ii][jj] + db[ii][jj]); }
		}
		if(SI(d) >= 3) {
			sort(ALL(d));
			setmin(ans, d[1] + d[2]);
		}
	}
	}
	
	{
		vector<int> d;
		inc(k, 4) {
			auto [f, ii, jj] = dd(h, w, ai, aj, k);
			if(f && s[ii][jj] == '.') { d.PB(dc[ii][jj]); }
		}
		if(SI(d) >= 2) {
			sort(ALL(d));
			setmin(ans, d[0] + d[1] + 2);
		}
	}
	
	if(ans == INF) { ans = -1; }
	out(ans);
}