def gcd(a,b):
    if b == 0:
        return a
    else:
        return gcd(b,a%b)

def lcm(a, b):
    return a * b // gcd (a, b)

N,M = map(int,input().split())
A = list(map(int,input().split()))
B = list(map(int,input().split()))

l = lcm(N,M)

A2 = A*(l//N)
B2 = B*(l//M)
ans = 10**18
for i in range(l):
    if A2[i] == B2[i]:
        ans = min(ans,i+1)

if ans == 10**18:
    print(-1)
else:
    print(ans)