#coding: utf-8
#yuki_6

def is_prime(n):
 i=2
 while i*i<=n:
  if n%i==0:
   return False
  i+=1
 return True
 
def fhash(n):
 v=n
 while v>=10:
  v=v/10+v%10
 return v

k=int(raw_input())
n=int(raw_input())

if k==1 or k==2: k=3
p=[]
h=[]

for i in xrange(k,n+1):
 if is_prime(i):
  p.append(i)
  h.append(fhash(i))

res=0
maxl=0
for i in xrange(len(p)):
 ref=[False]*10
 j=i
 while True:
  if j>=len(p): break
  if ref[h[j]]: break
  ref[h[j]]=True
  j+=1
 if maxl<=j-i:
  maxl=j-i
  res=p[i]
  
print res