used = [0] * 10

for x in range(10):
    used[x] = False

K = int(input())
N = int(input())
num = [2]
prime = []
prime1 = []

table = [True] * (N + 1)

for i in range(2, N + 1):
    if not table[i]:
        continue
    k = i + i
    while k < N + 1:
        table[k] = False
        k += i

    num.append(i)



for x in range(len(num)):
    if num[x] >= K and num[x] != 0:
        prime1.append(num[x])
        while num[x] >= 10:
            s = str(num[x])
            num[x] = 0
            for y in range(len(s)):
                num[x] += int(s[y])
        prime.append(num[x])

length = 0
start = 0
best_s = 0
best_l = 0

i = 0
while i < len(prime):
    if not used[prime[i]]:
        used[prime[i]] = True
        length += 1
        i += 1
    else:
        if start >= len(prime): break
        while start < i and prime[start] != prime[i]:
            used[prime[start]] = False
            start += 1
        start += 1
        length = i - start + 1
        i += 1

    best_l = max(best_l, length)
    if best_l == length:
        best_s = start

print(prime1[best_s])