#include "bits/stdc++.h"
using namespace std;
#define print(x) cout<<x<<endl;
#define rep(i,a,b) for(int i=a;i<b;i++)
#define REP(i,a) for(int i=0;i<a;i++)
#define printall(n,array) for(int i=0;i<n;i++){cout<<array[i]<<" ";}cout<<endl;
typedef long long ll;
typedef pair<int, int> PI;
typedef pair<int, PI> V;
typedef vector<int> VE;
const ll mod = 1000000007; //10^9+7

vector<int> prime;
bool is_prime[2000002];

int sieve(int k,int n){
  int p=0;
  REP(i,n+1)is_prime[i]=true;
  is_prime[0]=is_prime[1]=false;
  rep(i,2,n+1){
      if(is_prime[i]){
      ////print(i);///
      for(int j=2*i;j<=n;j+=i) is_prime[j]=false;
      if(i>=k)prime.push_back(i);
    }
  }
  return p;
}

int myhash(int h){
  //print("h "<<h);
  int sum=0;
  while(h){
    int dig=h%10;
    sum+=dig;
    h/=10;
  }
  if(sum>=10)sum=myhash(sum);
  //print("sum "<<sum);
  return sum;
}

int main(){
  int n,k;
  cin>>n;
  cin>>k;
  int p=sieve(n,k);
  //REP(i,prime.size())print(prime[i]);///
  //print("");///
  int s=0,t=0,res=0,start=0;
  map<int,int>count;
  while(s<prime.size()){
    //print("s "<<prime[s]);///
    while(t<prime.size()&&count[myhash(prime[t])]!=1){
      //print("t "<<prime[t]);///
      count[myhash(prime[t++])]++;
    }
    //for(auto itr = count.begin(); itr != count.end(); ++itr) {print(itr->first<<" "<<itr->second);}///
    //print("");///
    //print(prime[s]<<" "<<prime[t-1]);///
    if(res<=t-s){
      res=t-s;
      start=prime[s];
      //print("res "<<res);///
      //print("start "<<start);///
    }
    count[myhash(prime[s])]--;
    s++;
    //print("");///
  }
  print(start);
}