from functools import lru_cache

def prime_ls(k, n):
    ls = [False if i % 2 == 0 or i % 3 == 0 or i % 5 == 0 else True for i in range(n + 1)]
    ls[0] = ls[1] = False
    ls[2] = ls[3] = ls[5] = True

    for i in range(3, int(n**0.5) + 1, 2):
        for j in range(i**2, n + 1, i): 
            ls[j] = False
    
    return [p for p, is_prime in enumerate(ls[k:], k) if is_prime]

@lru_cache(maxsize=None)
def hash(n):
    s = str(n)
    return hash(sum([int(c) for c in s])) if len(s) >= 2 else n

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, hr = h_ls[l], 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)