def main():
    h, w = map(int, input().split())
    s = list(map(int, input().split()))
    s[0] -= 1
    s[1] -= 1
    g = list(map(int, input().split()))
    g[0] -= 1
    g[1] -= 1
    f = [list(input()) for i in range(h)]

    hr = [s+[0]]
    flag = True
    while flag:
        m = hr.pop(0)

        f[m[0]][m[1]] = "#"
        if (f[m[0]-1][m[1]]=="."):
            if not([m[0]-1, m[1], m[2]+1]in hr): hr.append([m[0]-1, m[1], m[2]+1])
        if f[m[0]+1][m[1]]==".":
            if not([m[0]+1, m[1], m[2]+1]in hr): hr.append([m[0]+1, m[1], m[2]+1])
        if f[m[0]][m[1]-1]==".":
            if not([m[0], m[1]-1, m[2]+1]in hr): hr.append([m[0], m[1]-1, m[2]+1])
        if f[m[0]][m[1]+1]==".":
            if not([m[0], m[1]+1, m[2]+1]in hr): hr.append([m[0], m[1]+1, m[2]+1])

        for n in hr[-4:]:
            if n[:2]==g:
                flag = False

    print(hr[-1][2])


if __name__=="__main__": main()