from collections import deque
from xml.dom import HierarchyRequestErr

H, W = map(int, input().split())
sx, sy, gx, gy = map(int, input().split())
sx -= 1
sy -= 1
gx -= 1
gy -= 1
S = []
for i in range(H):
    s = str(input())
    S.append(s)

calc_highest_x = [H - 1 for _ in range(W)]
highest_x = [[H - 1 for _ in range(W)] for _ in range(H)]
for i in reversed(range(H - 1)):
    for j in range(W):
        if S[i][j] == '#':
            calc_highest_x[j] = i
        highest_x[i][j] = calc_highest_x[j]

INF = 1 << 24

isvisited = [[False for _ in range(W)] for _ in range(H)]
dist = [[INF for _ in range(W)] for _ in range(H)]
dq = deque()
dq.appendleft([sx, sy])
dist[sx][sy] = 0

while len(dq):
    px, py = dq.popleft()
    if isvisited[px][py]:
        continue
    isvisited[px][py] = True

    if py - 1 >= 0:
        next_x = max(0, px - 1)
        next_x = highest_x[next_x][py - 1]
        dq.appendleft([next_x, py - 1])
        dist[next_x][py - 1] = min(dist[next_x][py - 1], dist[px][py])
    
    if py + 1 < W:
        next_x = max(0, px - 1)
        next_x = highest_x[next_x][py + 1]
        dq.appendleft([next_x, py + 1])
        dist[next_x][py + 1] = min(dist[next_x][py + 1], dist[px][py])

    
    if py - 2 >= 0:
        next_x = max(0, px - 1)
        next_x = highest_x[next_x][py - 2]
        dq.append([next_x, py - 2])
        dist[next_x][py - 2] = min(dist[next_x][py - 2], dist[px][py] + 1)

    if py - 2 >= 0:
        diffs_x = highest_x[px][py - 1] - px
        next_x = highest_x[px][py - 1] - 1 - diffs_x // 2
        next_x = highest_x[max(0, next_x)][py - 2]
        dq.appendleft([next_x, py - 2])
        dist[next_x][py - 2] = min(dist[next_x][py - 2], dist[px][py])

    if py + 2 < W:
        next_x = max(0, px - 1)
        next_x = highest_x[next_x][py + 2]
        dq.append([next_x, py + 2])
        dist[next_x][py + 2] = min(dist[next_x][py + 2], dist[px][py] + 1)

    if py + 2 < W:
        diffs_x = highest_x[px][py + 1] - px
        next_x = highest_x[px][py + 1] - 1 - diffs_x // 2
        next_x = highest_x[max(0, next_x)][py + 2]
        dq.appendleft([next_x, py + 2])
        dist[next_x][py + 2] = min(dist[next_x][py + 2], dist[px][py])

    if 0 <= py < W:
        next_x = max(0, px - 1)
        next_x = highest_x[next_x][py]
        dq.append([next_x, py])
        dist[next_x][py] = min(dist[next_x][py], dist[px][py] + 1)

if dist[gx][gy] == INF:
    print(-1)
else:
    print(dist[gx][gy])