#include <bits/stdc++.h>

#define REP(i,n) for(int i=0;i<(int)(n);i++)
#define ALL(x) (x).begin(),(x).end()

using namespace std;

bool prime[256000];

int func(int n) {
  if (n < 10) return n;
  int sum = 0;
  while (n > 0) {
    sum += n % 10;
    n /= 10;
  }
  return func(sum);
}

int main() {
  int K, N; cin >> K >> N;
  for (int i = 2; i <= N; ++i) prime[i] = true;
  for (int i = 2; i * i <= N; ++i) {
    if (!prime[i]) continue;
    for (int j = i * i; j <= N; j += i) prime[j] = false;
  }
  vector<int> v, w;
  for (int i = K; i <= N; ++i)
    if (prime[i]) v.push_back(i);
  for (int i : v) w.push_back(func(i));
  int ma = 0, pos = 0;
  REP(i,v.size()) {
    bool flag[10];
    REP(i,10) flag[i] = false;
    for (int j = i; j < (int)v.size(); ++j) {
      if (flag[w[j]]) break;
      flag[w[j]] = true;
      if (j - i + 1 >= ma) { pos = i; ma = j - i + 1; }
    }
  }
  cout << v[pos] << endl;
  return 0;
}