#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import array
import functools
import heapq
import math


def segment_sieve(begin, end, typecode="L"):
    assert begin > 0
    if begin == 1:
        begin = 2
    assert begin <= end
    sqrt_end = math.ceil(math.sqrt(end))
    is_prime_small = array.array("B", (True for i in range(sqrt_end)))
    is_prime_small[0] = False
    is_prime_small[1] = False
    is_prime = array.array("B", (True for i in range(end - begin)))
    for i in range(2, sqrt_end):
        if is_prime_small[i]:
            for j in range(2 * i, sqrt_end, i):
                is_prime_small[j] = False
            for k in range(max(2, (begin + i - 1) // i) * i, end, i):
                is_prime[k - begin] = False
    primes = array.array(typecode,
                         (i for (i, c) in enumerate(is_prime, begin) if c))
    return primes


@functools.lru_cache(maxsize=None)
def compute_hash(i):
    while i > 9:
        i = sum(divmod(i, 10))
    return i


def solve(k, n):
    primes = segment_sieve(k, n + 1)
    len_primes = len(primes)
    candidates = []
    for first in range(len_primes):
        last = first
        hash_values = {compute_hash(primes[first])}
        while last < len_primes - 1:
            last += 1
            new_hash_value = compute_hash(primes[last])
            if new_hash_value in hash_values:
                last -= 1
                break
            else:
                hash_values.add(new_hash_value)
        heapq.heappush(candidates, (-(last - first + 1), -primes[first]))
    (_, answer) = heapq.heappop(candidates)
    return -answer


def main():
    k = int(input())
    n = int(input())
    print(solve(k, n))


if __name__ == '__main__':
    main()