H, W = map(int, input().split())
S = [list(input()) for _ in range(H)]
T = [list(input()) for _ in range(H)]

S = [[1 if S[i][j] == '#' else 0 for j in range(W)] for i in range(H)]
T = [[1 if T[i][j] == '#' else 0 for j in range(W)] for i in range(H)]

a, b = 1, 1
for i in range(H):
    for j in range(W):
        a &= (S[i][j] + T[i][j] == 1)
        b &= (S[H - 1 - i][W - 1 - j] + T[i][j] == 1)

ans = 0.0
sp = 0.0
coef = 1.0

for k in range(1, 2020200):
    if k % 2:
        prob = (1.0 - sp) * a * (1.0 - coef)
    else:
        prob = (1.0 - sp) * b * (1.0 - coef)
    ans += prob * k
    sp += prob
    
    coef /= 2.0

print(ans)