from math import gcd
def crt(R,M):
	def ex_gcd(a,b,c):
		GCD=gcd(a,b)
		if GCD>1:
			if c%GCD!=0:
				return -1
			else:
				a//=GCD
				b//=GCD
				c//=GCD
		x1,y1,m=1,0,a
		x2,y2,n=0,1,b
		while m%n!=0:
			q=m//n
			x1,y1,m,x2,y2,n=\
			x2,y2,n,x1-q*x2,y1-q*y2,m-q*n
		return (x2*c,y2*c)

	N=len(M)
	for i in range(N-1):
		D=gcd(M[i],M[i+1])
		if (R[i+1]-R[i])%D!=0:
			return None
		P,Q=ex_gcd(M[i],M[i+1],D)
		ret=R[i]+M[i]*((R[i+1]-R[i])//D)*P
		ret%=M[i]*M[i+1]//D
		if i!=N-2:
			R[i+1]=ret
			M[i+1]=M[i]*M[i+1]//D
	return ret

n,m=map(int,input().split())
a=list(map(int,input().split()))
b=list(map(int,input().split()))
inf=10**18
ans=inf
for i in range(n):
	for j in range(m):
		if a[i]==b[j]:
			ret=crt([i,j],[n,m])
			ans=min(ans,ret+1)

if ans==inf:
	ans=-1

print(ans)