# coding:utf-8
import math
def hashf(n):
	while int(math.log10(n))!=0:
		m = int(math.log10(n)) + 1
		temp = 0
		for i in range(1, m+1):
			t = n%10
			temp += t
			n -= t
			n /= 10
		n = temp
	return n

def prime(k, n):
	res = []
	if k<=2 and 2<=n: res.append(2)
	for i in range(max(k, 2), n+1):
		for j in range(2, int(math.sqrt(i))+2):
			if i % j == 0:
				break
			if j == int(math.sqrt(i)+1):
				res.append(i)
	return res

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

array = prime(k, n)

array_hash = list(array)
for i in range(len(array)):
	array_hash[i] = hashf(array_hash[i])

inum = [0 for _ in range(10)]
leng = 0
ans = 0
r = 0

for l in range(len(array_hash)):
	while(r < len(array_hash) and inum[array_hash[r]]==0):
		inum[array_hash[r]]+=1
		r+=1
	if leng <= r-l:
		leng = r-l
		ans = array[l]
	inum[array_hash[l]]-=1

print ans