### BUGGY CODE ###


from collections import deque

h, w = map(int, input().split())
ch, cw = map(int, input().split())
dh, dw = map(int, input().split())

"""
l = [list(input().strip()) for i in range(h)]
ans = [[-1]*w for i in range(h)]
for i in range(h):
    for j in range(w):
        if l[i][j] == "#":
            ans[i][j] = -2
ch -= 1
cw -= 1
dh -= 1
dw -= 1
"""

base = ["#" * (w + 4)]
base.append("#" * (w + 4))
for n in range(h):
    base.append("##" + input() + "##")
base.append("#" * (w + 4))
base.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 base[i][j] == "#":
            ans[i][j] = -2
ch += 1
cw += 1
dh += 1
dw += 1

ans[ch][cw] = 0
move1 = [[1, 0], [-1, 0], [0, 1], [0, -1]]
move2 = [
        [-2, -2], [-2, -1], [-2, 0], [-2, 1], [-2, 2], [-1, -2], [-1, -1],
        [-1, 1], [-1, 2], [0, -2], [0, 2], [1, -2], [1, -1], [1, 1],
        [1, 2], [2, -2], [2, -1], [2, 0], [2, 1], [2, 2]
        ]
q1 = deque([[ch, cw]])
q2 = deque([])

while q1:
    x1, y1 = q1.popleft()
    q2.append([x1, y1])
    for i, j in move1:
        nx, ny = x1 + i, y1 + j
        """
        if nx < 0 or h <= nx or ny < 0 or w <= ny:
            continue
        """
        if ans[nx][ny] == -1:
            ans[nx][ny] = ans[x1][y1]
            q1.append([nx, ny])
    if len(q1) == 0:
        while q2:
            x2, y2 = q2.popleft()
            for i, j in move2:
                mx, my = x2 + i, y2 + j
                """
                if mx < 0 or h <= mx or my < 0 or w <= my:
                    continue
                """
                if ans[mx][my] == -1:
                    ans[mx][my] = ans[x2][y2] + 1
                    q1.append([mx, my])
print(ans[dh][dw])





### FIXED CODE ###


from collections import deque


def main():
    h, w = map(int, input().split())
    ch, cw = map(int, input().split())
    dh, dw = map(int, input().split())

    """
    l = [list(input().strip()) for i in range(h)]
    ans = [[-1]*w for i in range(h)]
    for i in range(h):
        for j in range(w):
            if l[i][j] == "#":
                ans[i][j] = -2
    ch -= 1
    cw -= 1
    dh -= 1
    dw -= 1
    """

    base = ["#" * (w + 4)]
    base.append("#" * (w + 4))
    for n in range(h):
        base.append("##" + input() + "##")
    base.append("#" * (w + 4))
    base.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 base[i][j] == "#":
                ans[i][j] = -2
    ch += 1
    cw += 1
    dh += 1
    dw += 1

    ans[ch][cw] = 0
    move1 = [[1, 0], [-1, 0], [0, 1], [0, -1]]
    move2 = [
        [-2, -2], [-2, -1], [-2, 0], [-2, 1], [-2, 2], [-1, -2], [-1, -1],
        [-1, 1], [-1, 2], [0, -2], [0, 2], [1, -2], [1, -1], [1, 1],
        [1, 2], [2, -2], [2, -1], [2, 0], [2, 1], [2, 2]
    ]
    q1 = deque([[ch, cw]])
    q2 = deque([])

    while q1:
        x1, y1 = q1.popleft()
        q2.append([x1, y1])
        for i, j in move1:
            nx, ny = x1 + i, y1 + j
            """
            if nx < 0 or h <= nx or ny < 0 or w <= ny:
                continue
            """
            if ans[nx][ny] == -1:
                ans[nx][ny] = ans[x1][y1]
                q1.append([nx, ny])
        if len(q1) == 0:
            while q2:
                x2, y2 = q2.popleft()
                for i, j in move2:
                    mx, my = x2 + i, y2 + j
                    """
                    if mx < 0 or h <= mx or my < 0 or w <= my:
                        continue
                    """
                    if ans[mx][my] == -1:
                        ans[mx][my] = ans[x2][y2] + 1
                        q1.append([mx, my])
    print(ans[dh][dw])


if __name__ == "__main__":
    main()