import math


def main():
    n, m = map(int, input().split())
    a = list(map(int, input().split()))
    b = list(map(int, input().split()))

    for i in range(m * n // math.gcd(m, n)):
        if a[i % n] == b[i % m]:
            exit(print(i + 1))
    print(-1)


if __name__ == "__main__":
    main()