import math

t = int(input())
for q in range(t):
    n, m = map(int, input().split())
    a = list(map(int, input().split()))
    b = list(map(int, input().split()))

    cnt1 = [0 for i in range(10010)]
    isexist = False
    for v in a:
        cnt1[v] += 1
    for v in b:
        if cnt1[v] > 0:
            isexist = True
            break

    if not isexist:
        print(-1)
        continue

    ans = -1
    loopnum = max(n, m) if max(n, m) % min(n, m) == 0 else n*m
    for i in range(loopnum):
        if a[i%n] == b[i%m]:
            ans = i+1
            break
    print(ans)