import math
INF=float('inf')
def lcm(a,b):
  return a*b//math.gcd(a,b)
def two_crt(mod1,mod2,i,j):
  g=math.gcd(mod1,mod2)
  if i%g!=j%g:
    return INF
  else:
    INV=pow(mod1//g,-1,mod2//g)
    return (i+(((j-i)//g)*mod1*INV))%lcm(mod1,mod2)
def crt(L):
  thismod=L[0][0]
  thisnum=L[0][1]
  for i in range(1,len(L)):
    thisnum=two_crt(thismod,L[i][0],thisnum,L[i][1])
    thismod=lcm(thismod,L[i][0])
  return thisnum,thismod

N,M=map(int,input().split())
L=list(map(int,input().split()))
R=list(map(int,input().split()))
ans=10**10
for i in range(N):
  for j in range(M):
    if L[i]==R[j]:
      a=two_crt(N,M,i,j)
      if a==INF:
        continue
      else:
        ans=min(ans,a)
if ans==10**10:
  print(-1)
else:
  print(ans+1)