from math import gcd
from numba import njit, i4

@njit(i4(i4, i4, i4, i4, i4, i4[:], i4[:]))
def main(n, m, g, m2, n2_inv, a, b):
    ans = 10 ** 9
    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)
            pass
    if ans == 10 ** 9:
        ans = -2
    return ans

import numpy as np
n, m = map(int, input().split())
g = gcd(n, m)
n2 = n // g
m2 = m // g
n2_inv = pow(n2, -1, m2)
a = np.array(list(map(int, input().split())), dtype=np.int32)
b = np.array(list(map(int, input().split())), dtype=np.int32)
ans = main(n, m, g, m2, n2_inv, a, b)
print(ans + 1)