def primes(n):
    if n < 1:
        return []

    is_prime = [True] * (n+1)
    is_prime[0] = False
    is_prime[1] = False
    for i in range(2, n+1):
        if not is_prime[i]:
            continue
        for j in range(i*2, n+1, i):
            is_prime[j] = False
    return [i for i in range(2, n+1) if is_prime[i]]

def main():
    """ main """
    # 1 N
    K = int(input())
    # 2 200000
    N = int(input())
    ps = sorted(set(primes(N)) - set(primes(K-1)))
    # しゃくとり
    shakutori = [ps[0]]
    # 答え
    ans = ps[0]
    # 最大長
    maxlength = 1

    for i in ps[1:]:
        for idx, j in enumerate(shakutori):
            if i%9 == j%9:
                shakutori = shakutori[idx+1:]

        shakutori.append(i)

        if maxlength <= len(shakutori):
            maxlength = len(shakutori)
            ans = shakutori[0]

    print(ans)


main()