from collections import deque

def Sieve(n): #n以下の素数全列挙(O(nloglogn)) retは素数が入ってる。divlisはその数字の素因数が一つ入ってる

    ret = []
    divlis = [-1] * (n+1) #何で割ったかのリスト(初期値は-1)
    
    flag = [True] * (n+1)
    flag[0] = False
    flag[1] = False

    ind = 2
    while ind <= n:

        if flag[ind]:
            ret.append(ind)

            ind2 = ind ** 2

            while ind2 <= n:
                flag[ind2] = False
                divlis[ind2] = ind
                ind2 += ind

        ind += 1

    return ret,divlis

def digsum(n):

    while n > 9:
        s = str(n)
        now = 0

        for i in s:
            now += int(i)

        n = now

    return n


K = int(input())
N = int(input())

rev,divs = Sieve(N)

lis = []

for i in rev:
    if i >= K:
        lis.append(i)

used = [False] * 10
useind = [None] * 10

ans = lis[0]
maxlen = 0

q = deque([])

for i in range(len(lis)):

    ds = digsum(lis[i])
    if not used[ds]:
        used[ds] = True
        useind[ds] = i
        q.append(lis[i])

    else:
        while q[0] != lis[useind[ds]]:
            pop = q.popleft()
            used[digsum(pop)] = False
        q.popleft()

        useind[ds] = i
        q.append(lis[i])

    if maxlen <= len(q):
        ans = q[0]
        maxlen = len(q)

    #print (q)

print (ans)