// includes
#include <cstdio>
#include <cstdint>
#include <iostream>
#include <iomanip>
#include <string>
#include <queue>
#include <stack>
#include <vector>
#include <set>
#include <map>
#include <unordered_map>
#include <algorithm>
#include <utility>
#include <functional>
#include <cmath>
#include <climits>
#include <bitset>
#include <list>
#include <random>

// macros
#define ll long long int
#define pb emplace_back
#define mk make_pair
#define pq priority_queue
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())

using namespace std;

//  types
typedef pair<int, int> P;
typedef pair<ll, int> Pl;
typedef pair<ll, ll> Pll;
typedef pair<double, double> Pd;
 
// constants
const int inf = 1e9;
const ll linf = 1LL << 50;
const double EPS = 1e-10;
const int mod = 1e9 + 7;

// solve
template <class T>bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;}
template <class T>bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;}

template <typename T>
vector<T> list_prime(T n){
  vector<T> res;
  vector<bool> i_prime = vector<bool>(n+1, true);
  for(ll i = 2; i <= n; i++){
    if(i_prime[i]){
      res.push_back(i);
      for(ll j = 2; j * i <= n; j++){
        i_prime[i * j] = false;
      }
    }
  }
  return res;
}

int f(int x){
  if(x < 10)return x;
  int tmp = x;
  int res = 0;
  while(tmp){
    res += tmp % 10;
    tmp /= 10;
  }
  return f(res);
}

int main(int argc, char const* argv[])
{
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int k, n;
  cin >> k >> n;
  auto pp = list_prime(n);
  vector<int> p;
  rep(i, sz(pp)){
    if(pp[i] >= k)p.pb(pp[i]);
  }
  vector<int> fp(sz(p));
  rep(i, sz(p))fp[i] = f(p[i]);
  int res = 1;
  int at = p[0];
  for(int i = 0; i < sz(p); i++){
    set<int> st;
    int tmp = 0;
    int curr = i;
    while(curr < sz(p)){
      if(st.find(fp[curr]) != st.end())break;
      tmp++;
      st.insert(fp[curr]);
      curr++;
    }
    if(tmp >= res){
      res = tmp;
      at = p[i];
    }
  }
  cout << at << endl;
	return 0;
}