def Eratosthenes(n):
    sieve = [True] * ((n + 1) // 2)
    for i in range(1, (int(n ** 0.5) + 1) // 2):
        if sieve[i]:
            for j in range(i * 3 + 1, (n + 1) // 2, i * 2 + 1):
                sieve[j] = False
    res = [i * 2 + 1 for i, s in enumerate(sieve) if s]
    res[0] = 2
    return res


def f(n):
    if n < 10:
        return n
    ret = sum(list(map(int, str(n))))
    return f(ret)


k = int(input())
n = int(input())
prime = Eratosthenes(n)
val = list()
for p in prime:
    val.append(f(p))

start = 0
for i in range(len(prime)):
    if prime[i] >= k:
        start = i
        break

used = [False] * 10
ans = prime[start]
maxlen = 0
right = start
for left in range(start, len(val)):
    while right < len(val) and used[val[right]] == False:
        used[val[right]] = True
        right += 1
    if maxlen <= right - left + 1:
        maxlen = right - left + 1
        ans = prime[left]

    if left == right:
        right += 1
    used[val[left]] = False

print(ans)