H,W=map(int,input().split())
S=[list(input()) for h in range(H)]
T=[list(input()) for h in range(H)]
for h in range(H):
    for w in range(W):
        S[h][w]=int(S[h][w]=="#")
        T[h][w]=int(T[h][w]=="#")
b0,b1=0,0
if all(S[h][w]+T[h][w]==1 for h in range(H) for w in range(W)):
    b0=1
if all(S[h][w]+T[H-1-h][W-1-w]==1 for h in range(H) for w in range(W)):
    b1=1
P=[0.5**i for i in range(100000)]
if b0:
    for i in range(1,100000,2):
        P[i]=1
if b1:
    for i in range(0,100000,2):
        P[i]=1
if b0==0 and b1==0:
    ans=-1
else:
    for i in range(1,100000):
        P[i]*=P[i-1]
    ans=sum(P)+1
print(ans)