#include <bits/stdc++.h>
#define int long long
#define x first
#define y second
#define getbit(x, i) (((x) >> (i)) & 1)
using namespace std;
typedef pair<int, int> pii;
#define hashset unordered_set
#define hashmap unordered_map
#define newline fast_writechar('\n')
#define unify(arr) arr.resize(unique(arr.begin(), arr.end()) - arr.begin())
#define getbit(x, i) (((x) >> (i)) & 1)

template <typename T>
vector<T> readvector(size_t sz) {
    vector<T> res(sz);
    for (size_t i = 0; i < sz; ++i) {
        cin >> res[i];
    }
    return res;
}
template <typename T>
std::ostream &operator<<(std::ostream &out, const std::vector<T> &v) {
    std::copy(v.begin(), v.end(), std::ostream_iterator<T>(out, " "));
    return out;
}

int mylog(int n) {
    return 63 - __builtin_clzll(n);
}

inline int binPow(int x, int deg, int mod) {
    int ans = 1;
    for (int i = sizeof(deg) * CHAR_BIT - 1; i >= 0; i--) {
        ans *= ans;
        ans %= mod;
        if (getbit(deg, i)) ans *= x;
        ans %= mod;
    }
    return ans;
}

/** Interface */

inline int readInt();
inline int readUInt();
inline void readWord(char *s);
inline int fast_readchar();  // you may use readchar() instead of it

inline void writeInt(int x);
inline void fast_writechar(int x);  // you may use putchar() instead of it
inline void writeWord(const char *s);
inline void fast_flush();

// ====================== END ======================
const int MAXN = 1e5 + 10;
const int MOD = 1e9 + 7;
const int INF = 1e18;
const int L = 1e6;

void solve() {
    int n = readInt(), m = readInt();
    int sx = readInt(), sy = readInt(), fx = readInt(), fy = readInt();
    sx--;
    sy--;
    fx--;
    fy--;
    auto on_board = [n, m](int x, int y) -> bool { return 0 <= x && x < n && 0 <= y && y < m; };
    char field[n][m];
    int dist[n][m];
    for (int i = 0; i < n; i++) {
        readWord(&field[i][0]);
        for (int j = 0; j < m; j++) {
            dist[i][j] = INF;
        }
    }
    dist[sx][sy] = 0;
    deque<pii> Q = {{sx, sy}};
    while (!Q.empty()) {
        auto v = Q.front();
        Q.pop_front();
        for (int dx = -1; dx <= 1; dx++) {
            for (int dy = -1; dy <= 1; dy++) {
                if (abs(dx) + abs(dy) == 1) {
                    int nx = v.x + dx;
                    int ny = v.y + dy;
                    if (!on_board(nx, ny)) continue;
                    if (field[nx][ny] == '.') {
                        if (dist[nx][ny] > dist[v.x][v.y]) {
                            dist[nx][ny] = dist[v.x][v.y];
                            Q.push_front({nx, ny});
                        }
                    }
                }
            }
        }
        for (int dx = -2; dx <= 2; dx++) {
            for (int dy = -2; dy <= 2; dy++) {
                int nx = v.x + dx;
                int ny = v.y + dy;
                if (!on_board(nx, ny)) continue;
                if (field[nx][ny] == '.') {
                    if (dist[nx][ny] > dist[v.x][v.y] + 1) {
                        dist[nx][ny] = dist[v.x][v.y] + 1;
                        Q.push_back({nx, ny});
                    }
                }
            }
        }
    }
    // for (int i = 0; i < n; i++) {
    //     for (int j = 0; j < m; j++) {
    //         // writeInt(dist[i][j]);
    //         // fast_writechar(field[i][j]);
    //         fast_writechar('\t');
    //     }   
    //         fast_writechar('\n');
    // }
    writeInt (dist[fx][fy] <= n * m ? dist[fx][fy] : -1ll) ;
    fast_writechar('\n');
}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    int t = 1;
    // cin >> t;
    for (int i = 1; i <= t; ++i) {
        // cout << "Case #" << i << ": ";
        solve();
    }
    fast_flush();
    return 0;
}

/** Read */

static const int buf_size = 4096;

inline int fast_readchar() {
    static char buf[buf_size];
    static int len = 0, pos = 0;
    if (pos == len) pos = 0, len = fread(buf, 1, buf_size, stdin);
    if (pos == len) return -1;
    return buf[pos++];
}

inline int readUInt() {
    int c = fast_readchar(), x = 0;
    while (c <= 32) c = fast_readchar();
    while ('0' <= c && c <= '9') x = x * 10 + c - '0', c = fast_readchar();
    return x;
}

inline int readInt() {
    int s = 1, c = fast_readchar();
    int x = 0;
    while (c <= 32) c = fast_readchar();
    if (c == '-') s = -1, c = fast_readchar();
    while ('0' <= c && c <= '9') x = x * 10 + c - '0', c = fast_readchar();
    return x * s;
}

inline void readWord(char *s) {
    int c = fast_readchar();
    while (c <= 32) c = fast_readchar();
    while (c > 32) *s++ = c, c = fast_readchar();
    *s = 0;
}

/** Write */

static int write_pos = 0;
static char write_buf[buf_size];

inline void fast_writechar(int x) {
    if (write_pos == buf_size) fwrite(write_buf, 1, buf_size, stdout), write_pos = 0;
    write_buf[write_pos++] = x;
}

inline void fast_flush() {
    if (write_pos) fwrite(write_buf, 1, write_pos, stdout), write_pos = 0;
}

inline void writeInt(int x) {
    if (x < 0) fast_writechar('-'), x = -x;

    char s[24];
    int n = 0;
    while (x || !n) s[n++] = '0' + x % 10, x /= 10;
    while (n--) fast_writechar(s[n]);
}

inline void writeWord(const char *s) {
    while (*s) fast_writechar(*s++);
}

Measured memory_bytes: 12596