T=int(input())

for _ in range(T):
    N,M=map(int,input().split())
    A=list(map(int,input().split()))
    B=list(map(int,input().split()))

    for i in range(N*M):
        if A[i%N]==B[i%M]:
            print(i+1)
            break
    else:
        print(-1)