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

x=math.lcm(n,m)

A=A*x
B=B*x
l=[]
for i in range(x):
    if A[i]==B[i]:
        print(i+1)
        exit()

print(-1)