def Eratosthenes(N): #N以下の素数のリストを返す
    #iが素数のときis_prime_list[i]=1，それ以外は0
    N+=1
    is_prime_list = [True]*N
#    is_prime_list[0], is_prime_list[1] = False, False #リストが必要なときはこの2行を有効化
#    for j in range(4,N,2): is_prime_list[j] = False
    m = int(N**0.5)+1
    for i in range(3,m,2):
        if is_prime_list[i]:
            is_prime_list[i*i::2*i]=[False]*((N-i*i-1)//(2*i)+1)
    return [2] + [i for i in range(3,N,2) if is_prime_list[i]]

# coding: utf-8
# Your code here!
import sys
readline = sys.stdin.readline
read = sys.stdin.read

#a,b,c = map(int,readline().split())

k = int(input())
n = int(input())
primes = [i for i in Eratosthenes(2*10**5) if k <= i <= n]
res = [i%9 for i in primes]

idx = n
val = 0
n = len(res)
s = set()
for i in range(n-1,-1,-1):
    cnt = 0
    for j in range(i,-1,-1):
        if res[j] not in s:
            cnt += 1
            s.add(res[j])
        else:
            #print(j,i,s)
            if val <= i-j:
                val = i-j
                idx = j+1
            break
    s.clear()    

#print(idx)
print(primes[idx])