from math import gcd
ans = 10 ** 18
n, m = map(int, input().split())
g = gcd(n, m)
n2 = n // g
m2 = m // g
n2_inv = pow(n2, -1, m2)
a = list(map(int, input().split()))
b = list(map(int, input().split()))
for i in range(n):
    for j in range(m):
        if (j - i) % g == 0 and a[i] == b[j]:
            k = n2_inv * (j - i) // g % m2
            ans = min(ans, i + k * n)
if ans == 10 ** 18:
    ans = -2
print(ans + 1)