from sys import stderr

K = int(input())
N = int(input())

isprime = [True] * (N + 1)
isprime[0] = isprime[1] = False
for i in range(2, N + 1):
	if isprime[i]:
		for j in range(i * 2, N + 1, i):
			isprime[j] = False

maxlen = len = 0
bkt = [-1] * 10
ans = 0

for i in range(K, N + 1):
	if not isprime[i]:
		continue
	h = i % 9
	if bkt[h] != -1:
		for j in range(10):
			rem = bkt[h]
			if 0 <= bkt[j] <= rem:
				bkt[j] = -1
				len -= 1
	bkt[h] = i
	len += 1
	if len >= maxlen:
		ans = min(v for v in bkt if v >= 0)
		maxlen = len

print(ans)