#include <bits/stdc++.h>
#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define FORR(i,a,b) for (int i=(a);i>=(b);i--)
#define pb push_back

using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef set<int> si;
const int inf = 1e9;
const int mod = 1e9+7;

vi pl;
bool is_prime(int a){
  if(a < 2)return false;
  for(vi::iterator itr = pl.begin(); itr != pl.end(); itr++){
    if(*itr * *itr > a)break;
    if(a % (*itr) == 0)return false;
  }
  return true;
}
int to_h(int a){
  if(a < 10)return a;
  while(a > 10){
    int s = 0;
    while(a > 0){
      s += a % 10;
      a /= 10;
    }
    a = s;
  }
  return a;
}
queue<int> q;
bool z[10];
main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  FOR(i, 2, 501){
    if(is_prime(i))pl.pb(i);
  }
  int maxl = 0, ans;
  int k, n;
  cin >> k >> n;
  FORR(i, n, k){
    if(!is_prime(i))continue;
    int h = to_h(i);
    if(z[h]){
      while(true){
        int f = q.front();
        q.pop();
        z[f] = false;
        if(f == h)break;
      }
    }
    q.push(h);
    z[h] = true;
    if(maxl < q.size()){
      maxl = q.size();
      ans = i;
    }
  }
  cout << ans << endl;
}