#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 1000000007;
// constexpr int MOD = 998244353;
constexpr int DY[]{1, 0, -1, 0}, DX[]{0, -1, 0, 1};
constexpr int DY8[]{1, 1, 0, -1, -1, -1, 0, 1}, DX8[]{0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U> inline bool chmax(T &a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U> inline bool chmin(T &a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

std::vector<int> prime_sieve(int n, bool get_only_prime) {
  std::vector<int> prime, smallest_prime_factor(n + 1);
  std::iota(smallest_prime_factor.begin(), smallest_prime_factor.end(), 0);
  for (int i = 2; i <= n; ++i) {
    if (smallest_prime_factor[i] == i) prime.emplace_back(i);
    for (int p : prime) {
      if (i * p > n || p > smallest_prime_factor[i]) break;
      smallest_prime_factor[i * p] = p;
    }
  }
  return get_only_prime ? prime : smallest_prime_factor;
}

int main() {
  constexpr int M = 10;
  int k, n; cin >> k >> n;
  vector<int> prime = prime_sieve(n, true);
  reverse(ALL(prime));
  while (prime.back() < k) prime.pop_back();
  reverse(ALL(prime));
  const int m = prime.size();
  vector<int> hash(m, 0);
  REP(i, m) {
    hash[i] = prime[i];
    while (hash[i] >= M) {
      int nxt = 0;
      for (char c : to_string(hash[i])) nxt = (nxt + c - '0');
      hash[i] = nxt;
    }
  }
  int s[M]{};
  vector<int> len(m, 0);
  int j = 0;
  REP(i, m) {
    while (j < m && s[hash[j]] == 0) ++s[hash[j++]];
    len[i] = j - i;
    --s[hash[i]];
  }
  const int longest = *max_element(ALL(len));
  for (int i = m - 1; i >= 0; --i) {
    if (len[i] == longest) {
      cout << prime[i] << '\n';
      return 0;
    }
  }
  assert(false);
}