#include <iostream>
#include <vector>
using namespace std;
bool sieve[2000001];
vector<int> primes;
int K, N;
int bad_hash(int t) {
  if(t < 10) return t;
  int r = 0;
  while(t > 0) {
    r += t % 10;
    t /= 10;
  }
  return bad_hash(r);
}
int main() {
  cin >> K >> N;
  sieve[0] = sieve[1] = true;
  for(long i = 2; i <= N; i++) {
    if(sieve[i]) continue;
    for(long j = i * i; j <= N; j += i) {
      sieve[j] = true;
    }
    if(i >= K) primes.push_back(i);
  }
  int start = 0;
  int max_len = 0;
  int answer = 0;
  vector<int> has(10);
  for(int end = 0; end < primes.size(); end++) {
    while(has[bad_hash(primes[end])]) {
      has[bad_hash(primes[start])] = false;
      start++;
    }
    has[bad_hash(primes[end])] = true;
    if(end - start + 1 >= max_len) {
      max_len = end - start + 1;
      answer = start;
    }
  }
  cout << primes[answer] << endl;
}