#include <bits/stdc++.h>
using namespace std;

//#define int long long
#define itn int
#define For(i, a, b) for (int i = (a); i <= static_cast<int>(b); i++)
#define Forr(i, a, b) for (int i = (a); i >= static_cast<int>(b); i--)
#define rep(i, n) For(i, 0, n - 1)
#define repall(i, arr) for (auto& i : (arr))
#define all(x) (x).begin(), (x).end()
#define pb push_back
#define dump(x) cerr << #x << " = " << (x) << '\n'
#define dump2(x, y) \
    cerr << #x << " = " << (x) << " " << #y << " = " << (y) << '\n'
#define SZ(x) ((int)(x).size())
#define bit(n) (1LL << (n))
constexpr int MOD = 1e9 + 7;

template <typename T>
using pq = priority_queue<T>;
template <typename T>
using pqr = priority_queue<T, vector<T>, greater<T>>;
const int INF = INT_MAX / 2;
using P = pair<int, int>;
using vec = vector<int>;
template <typename T>
using mat = vector<vector<T>>;

// clang-format off
template <typename T1, typename T2>
ostream& operator<<(ostream& stream, const pair<T1, T2>& p) { return stream << p.first << "," << p.second; }
template <typename T>
void print(const vector<T> vec) { rep (i, vec.size() - 1) cout << vec[i] << ' '; cout << vec[vec.size() - 1] << '\n'; }
template <typename Arg>
void print(const Arg arg) { cout << arg << '\n'; }
template <typename Head, typename... Args>
void print(const Head head, const Args... args) { cout << head << " "; print(args...); }
template <typename T, typename U>
void init(vector<T>& v, vector<U>& w) { rep (i, v.size()) cin >> v[i] >> w[i]; }
template <typename T>
void init(vector<T>& v) { rep (i, v.size()) cin >> v[i]; }
template <typename T>
T sum_(vector<T> vec, T init = 0) { return std::accumulate(all(vec), T(init)); }
template<typename T>
bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } return false; }
template<typename T>
bool chmin(T& a, const T& b) { if (a > b) { a = b; return true; } return false; }
template <typename T>
int index(const T& vec, const typename T::iterator it) { return distance(vec.begin(), it); }
template <typename T = int>
mat<T> mmat(int n, int m=0) { return mat<T>(n, vector<T>(m)); }
template <typename T = int>
vector<T> ivec(int n) { vector<T> v(n); init(v); return v; }
// clang-format on

void yn(bool tf) { print(tf ? "Yes" : "No"); }
void YN(bool tf) { print(tf ? "YES" : "NO"); }

int gcd(int a, int b) { return b ? gcd(b, a % b) : a; }
// -------------------------------------------------------------------
// sort 1 2 3 4
// pqr 1 2 3 must impl >
mat<char> s;
mat<int> dist;
int h, w;
int ch, cw, dh, dw;

bool in(int x, int y) {
    if (x >= 0 and x < h and y >= 0 and y < w) return true;
    return false;
}

signed main() {
    cin.tie(0), cout.tie(0), ios::sync_with_stdio(false);
    cin >> h >> w;
    cin >> ch >> cw >> dh >> dw;
    ch--, cw--, dh--, dw--;
    s = mmat<char>(h, w);
    rep (i, h)
        rep (j, w)
            cin >> s[i][j];

    dist = mmat<int>(h, w);
    rep (i, h)
        rep (j, w)
            dist[i][j] = INF;

    pqr<pair<int, P>> q;
    q.push({0, {ch, cw}});

    while (not q.empty()) {
        auto p = q.top();
        int d = p.first;
        auto [x, y] = p.second;
        q.pop();

        if (d >= dist[x][y]) continue;

        dist[x][y] = d;
        if (in(x + 1, y) and s[x + 1][y] == '.' and d < dist[x + 1][y])
            q.push({d, {x + 1, y}});
        if (in(x, y + 1) and s[x][y + 1] == '.' and d < dist[x][y + 1])
            q.push({d, {x, y + 1}});
        if (in(x - 1, y) and s[x - 1][y] == '.' and d < dist[x - 1][y])
            q.push({d, {x - 1, y}});
        if (in(x, y - 1) and s[x][y - 1] == '.' and d < dist[x][y - 1])
            q.push({d, {x, y - 1}});

        For(i, -2, 2) For(j, -2, 2) {
            if (i == 0 and j == 0) continue;
            if (i == 1 and j == 0) continue;
            if (i == -1 and j == 0) continue;
            if (i == 0 and j == 1) continue;
            if (i == 0 and j == -1) continue;
            if (in(x + i, y + j) and s[x + i][y + j] == '.' and
                (d + 1 < dist[x + i][y + j]))
                q.push({d + 1, {x + i, y + j}});
        }
    }

    if (dist[dh][dw] == INF)
        print(-1);
    else
        print(dist[dh][dw]);

    return 0;
}


Measured memory_bytes: 9048