import sys,copy
input=lambda:sys.stdin.readline().rstrip()
def has(a):
	if a<10:
		return a
	temp=0
	while a>0:
		temp+=a%10
		a//=10
	return has(temp)
K=int(input())
N=int(input())
isPrime=[1 for i in range(N+1)]
primes=[]
for i in range(2,N+1):
	if isPrime[i]:
		for j in range(i*2,N+1,i):
			isPrime[j]=0
		if K<=i:
			primes.append(i)
P=[has(i) for i in primes]
big,cur,ans=0,1,0
count=[0 for i in range(10)]
for end in range(len(P)):
	count[P[end]]+=1
	while max(count)>1:
		count[P[big]]-=1
		big+=1
	if cur<=end-big+1:
		cur=end-big+1
		ans=big
print(primes[ans])