import os
import sys

import numpy as np
from heapq import heappop, heappush


def solve(h, w, s, t, field):
    WARP = (-(w * 2 + 10), -(w * 2 + 9), -(w * 2 + 8), -(w * 2 + 7), -(w * 2 + 6),
            -(w + 6), -(w + 5), -(w + 3), -(w + 2),
            -2, 2,
            w + 2, w + 3, w + 5, w + 6,
            w * 2 + 6, w * 2 + 7, w * 2 + 8, w * 2 + 9, w * 2 + 10)
    WALK = (-(w + 4), -1, 1, w + 4)

    qc = np.zeros(1000000, dtype=np.int32)
    qv = np.zeros(1000000, dtype=np.int32)
    qv[0] = s
    l, r = 0, 1
    visited = np.zeros((h + 4) * (w + 4), np.int8)
    queued = np.zeros((h + 4) * (w + 4), np.int8)
    queued[s] = 1
    while l < r:
        cost = qc[l]
        v = qv[l]
        l += 1
        if v == t:
            return cost
        if visited[v]:
            continue
        visited[v] = 1
        for d in WALK:
            u = v + d
            if field[u] or visited[u] or queued[u]:
                continue
            queued[u] = 1
            l -= 1
            qc[l] = cost
            qv[l] = u
        for d in WARP:
            u = v + d
            if field[u] or visited[u] or queued[u]:
                continue
            qc[r] = cost + 1
            qv[r] = u
            r += 1

    return -1


if sys.argv[-1] == 'ONLINE_JUDGE':
    from numba.pycc import CC

    cc = CC('my_module')
    cc.export('solve', '(i8,i8,i8,i8,i1[:],)')(solve)
    cc.compile()
    exit()

if os.name == 'posix':
    # noinspection PyUnresolvedReferences
    from my_module import solve
else:
    from numba import njit

    solve = njit('(i8,i8,i8,i8,i1[:],)', cache=True)(solve)
    print('compiled', file=sys.stderr)

h, w = map(int, sys.stdin.readline().split())
ch, cw = map(int, sys.stdin.readline().split())
dh, dw = map(int, sys.stdin.readline().split())
field = np.ones((h + 4) * (w + 4), dtype=np.int8)
for i in range(h):
    line = sys.stdin.readline().strip()
    field[(i + 2) * (w + 4) + 2:(i + 2) * (w + 4) + w + 2] = list(map('.#'.index, line))
s = (ch + 1) * (w + 4) + cw + 1
t = (dh + 1) * (w + 4) + dw + 1
ans = solve(h, w, s, t, field)
print(ans)


### FIXED CODE ###

import os
import sys

import numpy as np
from heapq import heappop, heappush


def solve(h, w, s, t, field):
    WARP = (-(w * 2 + 10), -(w * 2 + 9), -(w * 2 + 8), -(w * 2 + 7), -(w * 2 + 6),
            -(w + 6), -(w + 5), -(w + 3), -(w + 2),
            -2, 2,
            w + 2, w + 3, w + 5, w + 6,
            w * 2 + 6, w * 2 + 7, w * 2 + 8, w * 2 + 9, w * 2 + 10)
    WALK = (-(w + 4), -1, 1, w + 4)

    q = [(0, s)]
    visited = np.zeros((h + 4) * (w + 4), np.int8)
    while q:
        cost, v = heappop(q)
        if v == t:
            return cost
        if visited[v]:
            continue
        visited[v] = 1
        for d in WALK:
            if field[v + d] or visited[v + d]:
                continue
            heappush(q, (cost, d + v))
        for d in WARP:
            if field[v + d] or visited[v + d]:
                continue
            heappush(q, (cost + 1, d + v))

    return -1


if sys.argv[-1] == 'ONLINE_JUDGE':
    from numba.pycc import CC

    cc = CC('my_module')
    cc.export('solve', '(i8,i8,i8,i8,i1[:],)')(solve)
    cc.compile()
    exit()

if os.name == 'posix':
    # noinspection PyUnresolvedReferences
    from my_module import solve
else:
    from numba import njit

    solve = njit('(i8,i8,i8,i8,i1[:],)', cache=True)(solve)
    print('compiled', file=sys.stderr)

h, w = map(int, sys.stdin.readline().split())
ch, cw = map(int, sys.stdin.readline().split())
dh, dw = map(int, sys.stdin.readline().split())
field = np.ones((h + 4) * (w + 4), dtype=np.int8)
for i in range(h):
    line = sys.stdin.readline().strip()
    field[(i + 2) * (w + 4) + 2:(i + 2) * (w + 4) + w + 2] = list(map('.#'.index, line))
s = (ch + 1) * (w + 4) + cw + 1
t = (dh + 1) * (w + 4) + dw + 1
ans = solve(h, w, s, t, field)
print(ans)