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

//#define int long long

typedef pair<int,int>pint;
typedef vector<int>vint;
typedef vector<pint>vpint;
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)
#define each(it,v) for(__typeof((v).begin()) it=(v).begin();it!=(v).end();it++)
template<class T,class U>void chmin(T &t,U f){if(t>f)t=f;}
template<class T,class U>void chmax(T &t,U f){if(t<f)t=f;}

vint prime;
bool f[200000];

int to(int v){
    int ret=0;
    while(true){
        while(v){
            ret+=v%10;
            v/=10;
        }
        if(ret<10)break;
        v=ret;
        ret=0;
    }
    return ret;
}

signed main(){
    fill_n(f,200000,true);f[0]=f[1]=false;
    reps(i,2,200000){
        if(!f[i])continue;
        prime.pb(i);
        for(int j=2;i*j<200000;j++)f[i*j]=false;
    }

    int K,N;cin>>K>>N;
    set<int>s;
    int hoge=0;
    while(prime[hoge]<K)hoge++;
    int l=hoge;
    int max_len=0,max_start=0;
    for(int i=hoge;i<prime.size()&&prime[i]<=N;i++){
        int tmp=to(prime[i]);
        while(s.find(tmp)!=s.end())s.erase(to(prime[l++]));
        if(max_len<=i-l+1){
            max_len=i-l+1;
            max_start=prime[l];
        }
        s.insert(tmp);
    }
    cout<<max_start<<endl;

    return 0;
}