#include <bits/stdc++.h>
using namespace std;

int main(){
	int K,N;cin>>K>>N;
	vector<bool> is_prime(N+1,true);
	vector<int> primes;
	for(int i=2;i<=N;i++){
		if(!is_prime[i]) continue;
		if(K<=i) primes.push_back(i);
		for(int j=2*i;j<=N;j+=i) is_prime[j]=false;
	}
	
	auto mhash=[](auto &&mhash,int n)->int{
		if(0<=n and n<9) return n;
		int t=0;
		while(n){t+=n%10;n/=10;}
		return mhash(mhash,t);
	};
	
	queue<int> que;
	int mlen=0,ans=0;
	vector<bool> v(10,false);
	for(auto p:primes){
		int t=mhash(mhash,p);
		while(v[t]){
			v[mhash(mhash,que.front())]=false;
			que.pop();
		}
		que.push(p);
		v[t]=true;
		if(mlen<=(int)que.size()){
			mlen=que.size();
			ans=que.front();
		}
	}
	cout<<ans<<"\n";
	return 0;
}