Trying not to

lol=open('input.txt','r')
height,width=lol.readline().split()
ax,ay=lol.readline().split()
bx,by=lol.readline().split()

a=[ ['X' for j in range(-1,int(width)+1)] for i in range(-1,int(height)+1)]

for i in range(1,int(height)+1):
    a[i][1:int(width)+1]=list(lol.readline())[:len(a[i])-2]

px=[-10 for j in range(int(width)*int(height))]
py=[-10 for j in range(int(width)*int(height))]










def YOBA(ax,bx,ay,by,H,W):
    dx=[1,0,-1,0]
    dy=[0,1,0,-1]
    stop=True
    d=0
    a[ax][ay]=0
    while 1==1:
        stopy=True
        for y in range(1,H+1):
            for x in range(1,W+1):
                if a[y][x]==d:
                    for k in range (0,4):
                        if a[y+dy[k]][x+dx[k]]=='.':
                            stopy=False
                            a[y+dy[k]][x+dx[k]]=d+1

        d=d+1

        if stopy or a[by][bx]=='X':
            break

    if (a[by][bx]=='X'):
        return False







    lene=a[bx][by]
    x=by
    y=bx
    d=lene

    while d>0:
        px[d]=x
        py[d]=y
        d=d-1
        for k in range(4):
            if a[y + dy[k]][x + dx[k]]==d:
                x=x+dx[k]
                y=y+dy[k]
                break

    px[0]=ax
    py[0]=ay
    return True



d=0
try:
    if YOBA(int(ax)+1,int(bx)+1,int(ay)+1,int(by)+1,int(height),int(width)):
        for i in range(len(px)):
            if px[i]>-1:
                d=d+1
        print(d-1)
    else:
        print(-1)
except:
    print(-1)