h, w = list(map(int, input().split()))
sy, sx = list(map(lambda x: int(x)-1, input().split()))
gy0, gx0, gy1, gx1 = list(map(lambda x: int(x), input().split()))
gy0, gx0 = gy0-1, gx0-1
ty, tx = list(map(lambda x: int(x)-1, input().split()))
dp = [[[-1, -1, -1] for _ in range(w)] for _ in range(h)]
dp[sy][sx][0] = 0
B = [(sy, sx, 0)]
c = 0
while A:= B:
    B = []
    while A:
        y, x, a = A.pop()
        if not a and gy0 <= y < gy1 and gx0 <= x < gx1 and dp[y][x][1] == -1:
            dp[y][x][1] = c
            A.append((y, x, 1))
        if a == 1 and y == ty and x == tx and dp[y][x][2] == -1:
            dp[y][x][2] = c
            A.append((y, x, 2))
        for ny, nx in [(y, x-1), (y, x+1), (y-1, x), (y+1, x)]:
            if 0 <= ny < h and 0 <= nx < w and dp[ny][nx][a] == -1:
                dp[ny][nx][a] = c+1
                B.append((ny, nx, a))
    c += 1
print(dp[sy][sx][2])