from functools import lru_cache

def prime_ls(k, n):
    ls = [i for i in range(max(2, k), n + 1) if i == 2 or not i % 2 == 0]
    for i in range(3, int(n**0.5) + 1, 2):
        ls = [j for j in ls if j == i or not j % i == 0]
    return ls

@lru_cache(maxsize=None)
def hash(n):
    if n // 10 == 0:
        return n
    s = str(n)
    return hash(sum([int(c) for c in s]))

k = int(input())
n = int(input())

p_ls = prime_ls(k, n)
h_ls = [hash(p) for p in p_ls]

l, r = 0, 0
max_len = 0

memo = [False] * 10

while r < len(h_ls):
    hl = h_ls[l]
    hr = h_ls[r]
    if memo[hr]:
        memo[hl] = False
        l += 1
    else:
        memo[hr] = True
        r += 1
    
    lr_len = r - l
    if lr_len >= max_len:
        max_len = lr_len
        ans = p_ls[l]

print(ans)