K = int(input())
N = int(input())
prime = [True] * (N + 1)
prime[0], prime[1] = False, False
for i in range(2, N + 1):
	if prime[i]:
		for j in range(i * 2, N + 1, i):
			prime[j] = False
ML = 0
ans = -1
primelist = list(filter(lambda x: prime[x], range(K, N + 1)))
for i in range(len(primelist)):
	B = 0
	P = i
	while P < len(primelist):
		if ((B >> (primelist[P] % 9)) & 1) == 1:
			break
		B |= 1 << (primelist[P] % 9)
		P += 1
	if ML <= P - i:
		ML = P - i
		ans = primelist[i]
print(ans)