from collections import defaultdict

def sieve(n):
    is_prime = [True] * (n+1)
    is_prime[0] = is_prime[1] = False
    for j in range(4, n+1, 2):
        is_prime[j] = False
    prime = [2]
    for i in range(3, n+1):
        if is_prime[i]:
            prime.append(i)
            for j in range(i*i, n+1, 2*i):
                is_prime[j] = False
    return prime

def digitsum(s):
    if len(s) == 1:
        return int(s)
    return digitsum(str(sum(map(int, s))))

K = int(input())
N = int(input())
prime = sieve(N)
num = []
val = []
for p in prime:
    if p >= K:
        num.append(p)
        val.append(digitsum(str(p)))
last = defaultdict(lambda: -1)
ans = (1, 0)
left = 0
last[val[0]] = 0
for i in range(1, len(val)):
    if last[val[i]] >= left:
        left = last[val[i]] + 1
    last[val[i]] = i
    ans = max(ans, (i - left + 1, left))
print(num[ans[1]])