### BUGGY CODE ###

import sys
import numpy as np
 
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
 
def main(wall, Sx, Sy, Tx, Ty):
    INF = 1 << 30
    H, W = wall.shape
    S = Sx * W + Sy
    T = Tx * W + Ty
    dist = np.full(H * W, INF, np.int64)
    deq = np.empty(H * W + 100, np.int64)
    dist[S] = 0
    deq[0], l, r = S, 0, 1
    while l < r:
        v, l = deq[l], l + 1
        vx, vy = divmod(v, W)
        # そのままあるく
        for dx, dy in ((1, 0), (0, 1), (-1, 0), (0, -1)):
            wx, wy = vx + dx, vy + dy
            if not (0 <= wx < H):
                continue
            if not (0 <= wy < W):
                continue
            if wall[wx, wy]:
                continue
            w = wx * W + wy
            if dist[w] <= dist[v]:
                continue
            dist[w] = dist[v]
            deq[l - 1], l = w, l - 1
        # ワープする
        for dx in range(-2, 3):
            for dy in range(-2, 3):
                wx, wy = vx + dx, vy + dy
                if not (0 <= wx < H):
                    continue
                if not (0 <= wy < W):
                    continue
                if wall[wx, wy]:
                    continue
                w = wx * W + wy
                if dist[w] <= dist[v] + 1:
                    continue
                dist[w] = dist[v] + 1
                deq[r], r = w, r + 1
    ans = dist[T]
    if ans == INF:
        ans = -1
    return ans


H, W = map(int, readline().split())
Sx, Sy = map(lambda x: int(x) - 1, readline().split())
Tx, Ty = map(lambda x: int(x) - 1, readline().split())
wall = np.frombuffer(read(), 'S1').reshape(H, -1)[:, :W] == b'#'

print(main(wall, Sx, Sy, Tx, Ty))

### FIXED CODE ###

#写経
#https://atcoder.jp/contests/abc176/submissions/16141246

import sys
import numpy as np
import numba
from numba import njit, b1, i4, i8, f8
 
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
 
@njit((b1[:, :], i8, i8, i8, i8), cache=True)
def main(wall, Sx, Sy, Tx, Ty):
    INF = 1 << 30
    H, W = wall.shape
    S = Sx * W + Sy
    T = Tx * W + Ty
    dist = np.full(H * W, INF, np.int64)
    deq = np.empty(H * W + 100, np.int64)
    dist[S] = 0
    deq[0], l, r = S, 0, 1
    while l < r:
        v, l = deq[l], l + 1
        vx, vy = divmod(v, W)
        # そのままあるく
        for dx, dy in ((1, 0), (0, 1), (-1, 0), (0, -1)):
            wx, wy = vx + dx, vy + dy
            if not (0 <= wx < H):
                continue
            if not (0 <= wy < W):
                continue
            if wall[wx, wy]:
                continue
            w = wx * W + wy
            if dist[w] <= dist[v]:
                continue
            dist[w] = dist[v]
            deq[l - 1], l = w, l - 1
        # ワープする
        for dx in range(-2, 3):
            for dy in range(-2, 3):
                wx, wy = vx + dx, vy + dy
                if not (0 <= wx < H):
                    continue
                if not (0 <= wy < W):
                    continue
                if wall[wx, wy]:
                    continue
                w = wx * W + wy
                if dist[w] <= dist[v] + 1:
                    continue
                dist[w] = dist[v] + 1
                deq[r], r = w, r + 1
    ans = dist[T]
    if ans == INF:
        ans = -1
    return ans

H, W = map(int, readline().split())
Sx, Sy = map(lambda x: int(x) - 1, readline().split())
Tx, Ty = map(lambda x: int(x) - 1, readline().split())
wall = np.frombuffer(read(), 'S1').reshape(H, -1)[:, :W] == b'#'

print(main(wall, Sx, Sy, Tx, Ty))