from time import time
start_time = time()

def extgcd(a, b):
    if b == 0:
        return 1, 0, a
    q, r = divmod(a, b)
    x, y, d = extgcd(b, r)
    s, t = y, x-q*y
    return s, t, d

def MOD(a, m):
    return (a%m + m)%m;

def CRT_list(b, m):
    # b: list
    # m: list
    # x ≡ bi (mod mi)を満たすx ≡ r (mod lcm(m1*m2..*mn))について
    # r, lcm(m1*m2..*mn)をreturn
    # 解無しの場合は0, -1をreturn
    r, M = 0, 1
    for i in range(len(b)):
        p, q, d = extgcd(M, m[i])
        if (b[i]-r)%d != 0:
            return 0, -1
        temp = (b[i]-r)//d * p % (m[i]//d)
        r += M * temp
        M *= m[i]//d
    return MOD(r, M), M

import math
from functools import reduce
def lcm_base(x, y):
  return (x * y) // math.gcd(x, y)

def lcm_list(numbers):
  return reduce(lcm_base, numbers, 1)

import sys
import io, os
input = sys.stdin.buffer.readline
#input = io.BytesIO(os.read(0,os.fstat(0).st_size)).readline

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

N = 5000
INF = 10**18
res = INF
P = []
from collections import defaultdict
D = defaultdict(lambda: [])
for j, b in enumerate(B):
    D[b].append(j)

for i, a in enumerate(A):
    for j in D[a]:
        if i == j:
            if i <= res:
                res = i
            break
        else:
            P.append(5000*i+j)

m = [n, m]
TIME_LIMIT = 1.9
for x in P:
    now_time = time()
    if now_time - start_time > TIME_LIMIT:
        break
    i, j = divmod(x, 5000)
    b = [i, j]
    r, M = 0, 1
    for i in range(len(b)):
        p, q, d = extgcd(M, m[i])
        if (b[i]-r)%d != 0:
            r, M = 0, -1
            break
        temp = (b[i]-r)//d * p % (m[i]//d)
        r += M * temp
        M *= m[i]//d
    if M != -1:
        if r <= res:
            res = r
if res != INF:
    print(res+1)
else:
    print(-1)