def extgcd(a, b):
    # ax + by = gcd(a,b)
    # return gcd(a,b), x, y
    if a == 0:
        return b, 0, 1
    else:
        g, x, y = extgcd(b % a, a)
        return g, y - (b // a) * x, x

def chineseRem(b1, m1, b2, m2):
    # x ≡ b1 (mod m1) ∧ x ≡ b2 (mod m2) <=> x ≡ r (mod m)
    # となる(r. m)を返す
    # 解無しのとき(0, -1)
    d, p, q = extgcd(m1, m2)
    if (b2 - b1) % d != 0:
        return 0, -1
    m = m1 * (m2 // d)  # m = lcm(m1, m2)
    tmp = (b2-b1) // d * p % (m2 // d)
    r = (b1 + m1 * tmp) % m
    return r, m

n,m = map(int,input().split())
ans = 10**10
A = list(map(int,input().split()))
B = list(map(int,input().split()))

for i,a in enumerate(A):
    for j,b in enumerate(B):
        if a != b:
            continue
        r,m = chineseRem(i,n,j,m)
        if m > 0:
            ans = min(ans,r+1)
if ans == 10**10:
    ans = -1
print(ans)