N = 200200
X = [-1] * (N+1)
L = [{} for _ in range(N+1)]
k = 2
while k <= N:
    X[k] = 1
    L[k][k] = 1
    for i in range(k*2, N+1, k):
        X[i] = 0
        L[i][k] = 1
    d = 2
    while k**d <= N:
        for i in range(k**d, N+1, k**d):
            L[i][k] += 1
        d += 1
    while k <= N and X[k] >= 0:
        k += 1
P = [i for i in range(N+1) if X[i] == 1]

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

for i in range(200200):
    if P[i] >= K:
        i0 = i
        break

ma = -1
ans = -1
for i, p in enumerate(P):
    if p < K: continue
    if p > N: break
    s = 0
    for j in range(i, i + 11):
        t = 1 << (P[j] % 9)
        if s & t or P[j] > N:
            if j - i >= ma:
                ma = j - i
                ans = P[i]
            break
        s |= t

print(ans)