k = int(input())
n = int(input())
sieve = [True] * (n + 1)
primes = []
for p in range(2, n + 1):
    if sieve[p]:
        if p >= k:
            primes.append(p)
        for i in range(p * p, n + 1, p):
            sieve[i] = False
seen = [False] * 10
mx = 0
now = 0
from collections import deque
q = deque()
for p in primes:
    po = p
    while p >= 10:
        p = sum(map(int, str(p)))
    while seen[p]:
        i, _ = q.popleft()
        seen[i] = False
        now -= 1
    q.append((p, po))
    seen[p] = True
    now += 1
    if now >= mx:
        ans = q[0][1]
        mx = now
print(ans)