### BUGGY CODE ###

#---------------------------------[インポート]---------------------------------#
from collections import deque
#---------------------------------[入力受取・初期設定]---------------------------------#
H, W = map(int, input().split())
C = tuple(map(int, input().split())) # 魔法の位置
D = tuple(map(int, input().split())) # ゴール
D_y = D[0] -1 # 0スタート
D_x = D[1] -1 # 0スタート
S = [list(input()) for _ in range(H)]
visited = [[-1] * W for _ in range(H)]
visited[C[0]-1][C[1]-1] = 0 # 初期値
moves = [(1, 0), (0, 1), (-1, 0), (0, -1)] # 普通の移動
main_q = deque()
magic_q = deque() # マジック用のキュー
main_q.append((C[0]-1, C[1]-1))
#---------------------------------[BFS]---------------------------------#
while main_q:
    y, x = main_q.popleft()
    magic_q.append((y, x))
    for move in moves:
        dy, dx = move
        moved_y = y + dy
        moved_x = x + dx

        if moved_y < 0 or H -1 < moved_y or moved_x < 0 or W -1 < moved_x:
            continue
        if S[moved_y][moved_x] == '#':
            continue
        if S[moved_y][moved_x] == '.' and visited[moved_y][moved_x] == -1:
            main_q.append((moved_y, moved_x))
            visited[moved_y][moved_x] = visited[y][x]
    #---------------------------------[マジック用のBFS]---------------------------------#
    if not main_q: # main_qが空になった場合は探索済みからマジックを使う
        while magic_q:
            y, x = magic_q.popleft()
            for dy in range(-2, 3):
                for dx in range(-2, 3):
                    moved_y = y + dy
                    moved_x = x + dx

                    if moved_y < 0 or H -1 < moved_y or moved_x < 0 or W -1 < moved_x:
                        continue
                    if S[moved_y][moved_x] == '#':
                        continue
                    if S[moved_y][moved_x] == '.' and visited[moved_y][moved_x] == -1:
                        main_q.append((moved_y, moved_x))
                        visited[moved_y][moved_x] = visited[y][x] + 1
#---------------------------------[回答表示]---------------------------------#
answer = visited[D_y][D_x]
print(answer)

### FIXED CODE ###

import sys
input = sys.stdin.readline


def main():
    h, w = map(int, input().split())
    ch, cw = map(int, input().split())
    dh, dw = map(int, input().split())
    
    ch += 1
    cw += 1
    dh += 1
    dw += 1
    
    
    s = ["#"*(w+4)]
    s.append("#"*(w+4))
    for i in range(h):
        s.append("##" + input()[:-1] + "##")
    s.append("#"*(w+4))
    s.append("#"*(w+4))
    
    
    ans = [[-1]*(w+4) for _ in range(h+4)]
    for i in range(h+4):
        for j in range(w+4):
            if s[i][j] == "#":
                ans[i][j] = -2
    ans[ch][cw] = 0
    
    move = [(-1, 0), (1, 0), (0, -1), (0, 1)]
    move2 = [(-2, -2), (-2, -1), (-2, 0), (-2, 1), (-2, 2), \
             (-1, -2), (-1, -1), (-1, 0), (-1, 1), (-1, 2), \
             (0, -2), (0, -1), (0, 0), (0, 1), (0, 2), \
             (1, -2), (1, -1), (1, 0), (1, 1), (1, 2), \
             (2, -2), (2, -1), (2, 0), (2, 1), (2, 2)]
        
    not_yet = [(ch, cw)]
    one_time = []
    
    while len(not_yet) > 0:
        x, y = not_yet.pop()
        one_time.append((x, y))
        for (p, q) in move:
            v1, v2 = x+p, y+q
            if ans[v1][v2] == -1:
                not_yet.append((v1, v2))
                ans[v1][v2] = ans[x][y]
                
        if len(not_yet) == 0:
            while len(one_time) > 0:
                x2, y2 = one_time.pop()
                for (v1, v2) in move2:
                    i, j = x2+v1, y2+v2
                    if ans[i][j] == -1:
                        ans[i][j] = ans[x2][y2]+1
                        not_yet.append((i, j))
          
    print(ans[dh][dw])
    
    
    
if __name__ == "__main__":
    main()