#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using Edge = int;
using Graph = vector<vector<Edge>>;
#define REP(i, n) for (int i = 0; i < (n); ++i)
#define SORT(v) sort((v).begin(), (v).end())
#define RSORT(v) sort((v).rbegin(), (v).rend())
const ll MOD = 1000000007;
const ll nmax = 8;
const ll INF = 1e13;
const int MAX = 510000;
bool graph[nmax][nmax];
long long fac[MAX], finv[MAX], inv[MAX];

void COMinit()
{
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++)
    {
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}

ll COM(int n, int k)
{
    if (n < k)
        return 0;
    if (n < 0 || k < 0)
        return 0;

    return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}

vector<vector<ll>> dist = vector<vector<ll>>(nmax, vector<ll>(nmax, INF));
struct SegmentTree
{
private:
    ll n;
    vector<ll> node;

public:
    SegmentTree(vector<ll> v)
    {
        ll sz = v.size();
        n = 1;
        while (n < sz)
        {
            n *= 2;
        }
        node.resize(2 * n - 1, INF);

        for (ll i = 0; i < sz; i++)
        {
            node[i + n - 1] = v[i];
        }

        for (ll i = n - 2; i >= 0; i--)
        {
            node[i] = min(node[2 * i + 1], node[2 * i + 2]);
        }
    }
    void update(ll x, ll val)
    {
        x += (n - 1);
        node[x] = val;
        while (x > 0)
        {
            x = (x - 1) / 2;
            node[x] = min(node[2 * x + 1], node[2 * x + 2]);
        }
    }

    // findは半開区間で考える
    ll find(ll a, ll b, ll k = 0, ll l = 0, ll r = -1)
    {
        if (r < 0)
            r = n;

        if (r <= a || b <= l)
            return INF;

        if (a <= l && r <= b)
            return node[k];

        ll vl = find(a, b, 2 * k + 1, l, (l + r) / 2);
        ll vr = find(a, b, 2 * k + 2, (l + r) / 2, r);
        return min(vl, vr);
    }
};
void warshall_floyd(ll n)
{
    for (size_t i = 0; i < n; i++)
    {
        for (size_t j = 0; j < n; j++)
        {
            for (size_t k = 0; k < n; k++)
            {
                dist[j][k] = min(dist[j][k], dist[j][i] + dist[i][k]);
            }
        }
    }
}

class UnionFind
{
public:
    vector<ll> Parent;

    UnionFind(ll N)
    {
        Parent = vector<ll>(N, -1);
    }
    ll find(ll A)
    {
        if (Parent[A] < 0)
            return A;
        return Parent[A] = find(Parent[A]);
    }

    ll size(ll A)
    {
        return -Parent[find(A)];
    }

    bool Union(ll A, ll B)
    {
        A = find(A);
        B = find(B);
        if (A == B)
        {
            return false;
        }
        if (size(A) < size(B))
            swap(A, B);

        Parent[A] += Parent[B];
        Parent[B] = A;

        return true;
    }
};

ll gcd(ll a, ll b)
{
    if (b == 0)
        return a;
    return gcd(b, a % b);
}

ll lcm(ll a, ll b)
{
    ll g = gcd(a, b);
    return a / g * b;
}

ll mulMod(ll a, ll b)
{
    return (((a % MOD) * (b % MOD)) % MOD);
}

ll powMod(ll a, ll p)
{
    if (p == 0)
    {
        return 1;
    }
    else if (p % 2 == 0)
    {
        ll half = powMod(a, p / 2);
        return mulMod(half, half);
    }
    else
    {
        return mulMod(powMod(a, p - 1), a);
    }
}

ll ceil(ll a, ll b)
{
    return (a + b - 1) / b;
}

vector<ll> tsort(Graph G)
{
    ll N = G.size();
    vector<ll> in(N);
    for (auto &&edges : G)
    {
        for (auto &&edge : edges)
        {
            in[edge]++;
        }
    }

    queue<int> que;

    for (int i = 0; i < N; i++)
    {
        if (in[i] == 0)
        {
            que.push(i);
        }
    }
    int cnt = 0;
    vector<ll> ans;
    while (!que.empty())
    {
        int v = que.front();
        que.pop();
        ans.push_back(v);
        for (auto &&next : G[v])
        {

            in[next]--;
            if (in[next] == 0)
            {
                que.push(next);
            }
        }
    }
    return ans;
}

const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
ll cost[1010][1010];
char field[1010][1010];
bool walk_seen[1010][1010];
bool warp_seen[1010][1010];
// Generated by 1.1.7.1 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
int main()
{
    ll H, W;
    cin >> H >> W;
    ll ch, cw, dh, dw;
    cin >> ch >> cw >> dh >> dw;
    --ch;
    --cw;
    --dh;
    --dw;
    for (int i = 0; i < H; i++)
    {
        string str;
        cin >> str;
        for (int j = 0; j < W; j++)
        {
            field[i][j] = str[j];
            cost[i][j] = INF;
            walk_seen[i][j] = false;
            warp_seen[i][j] = false;
        }
    }
    deque<pair<ll, ll>> que;
    que.push_front(make_pair(ch, cw));
    cost[ch][cw] = 0;
    walk_seen[ch][cw] = true;
    warp_seen[ch][cw] = true;
    while (!que.empty())
    {
        pair<ll, ll> pos = que.front();
        que.pop_front();
        ll x = pos.first;
        ll y = pos.second;
        for (int dir = 0; dir < 4; dir++)
        {
            ll nx = x + dx[dir];
            ll ny = y + dy[dir];
            if (nx < 0 || ny < 0 || nx >= H || ny >= W)
                continue;
            if (field[nx][ny] == '#')
                continue;
            if (walk_seen[nx][ny])
                continue;

            // 歩いて来れる場合はコストはどちらかのmin
            walk_seen[nx][ny] = true;
            cost[nx][ny] = min(cost[nx][ny], cost[x][y]);
            que.push_front(make_pair(nx, ny));
        }

        for (int dx = -2; dx <= 2; dx++)
        {
            for (int dy = -2; dy <= 2; dy++)
            {
                ll nx = x + dx;
                ll ny = y + dy;
                if (nx < 0 || ny < 0 || nx >= H || ny >= W)
                    continue;
                if (field[nx][ny] == '#')
                    continue;
                if (warp_seen[nx][ny])
                    continue;
                warp_seen[nx][ny] = true;
                cost[nx][ny] = min(cost[nx][ny], cost[x][y] + 1);
                que.push_back(make_pair(nx, ny));
            }
        }
    }
    if(cost[dh][dw] == INF){
        cout << -1 << endl;
    }else{
        cout << cost[dh][dw] << endl;
    }

    return 0;
}


Measured memory_bytes: 14504