h, w = map(int, input().split())
s = [input() for _ in range(h)]
t = [input() for _ in range(h)]
ok = all(s[i][j] != t[i][j] for i in range(h) for j in range(w))
if ok:
    ans = 0.0
    p = 1.0
    ans += p
    d = 2
    while p:
        ans += 2 * p
        for _ in range(d):
            p /= 2
        d += 2
    print(f'{ans:.16f}')
else:
    ans = 0.0
    p = 1.0
    d = 1
    while p:
        ans += 2 * p
        for _ in range(d):
            p /= 2
        d += 2
    print(f'{ans:.16f}')