def sieve(k, n):
    res = []
    is_prime = [True] * (n + 1)
    
    for i in xrange(2, n + 1):
        if is_prime[i]:
            if i >= k:
                res.append(i)

            for j in xrange(i * i, n + 1, i):
                is_prime[j] = False

    return res

def frank_hash(n):
    if n < 10:
        return n

    return frank_hash(sum(map(int, str(n))))

k = input()
n = input()

primes = sieve(k, n)
hashes = map(frank_hash, primes)

exists = [False] * 10

max_length = -1
ans = -1

l = 0
for r in xrange(len(primes)):
    while exists[hashes[r]]:
        exists[hashes[l]] = False
        l += 1

    exists[hashes[r]] = True
    if max_length <= r - l + 1:
        max_length = r - l + 1
        ans = primes[l]

print ans