#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

/*
    Max_Prime以下の素数をprimes[]に格納
*/

const int Max_Prime = 1000000;
int tmp_primes[Max_Prime];
vector<int> primes;

void PrimeInit() {
    rep(i,Max_Prime)tmp_primes[i] = 1;
    tmp_primes[0] = 0;
    tmp_primes[1] = 0;

    rep(i,Max_Prime){
        if(tmp_primes[i] == 0)continue;
        int j = 2;
        while(i * j < Max_Prime){
            tmp_primes[i*j] = 0;
            j++;
        }
    }
    
    rep(i,Max_Prime){
        if(tmp_primes[i])primes.push_back(i);
    }
}

int suujikonn(ll x){
    if(x < 0) return -1;
    else if(x == 0) return 0;
    else if(x % 9 == 0) return 9;
    else return x % 9;
}

int main() {
    int k, n;
    cin >> k >> n;
    PrimeInit();

    int ma = 0;
    int ans = 0;

    int m = primes.size();
    int f[m] = {};
    int cnt[10] = {};
    int l = 0;
    int now = 0;

    rep(i,m){
        int x = primes[i];
        if(x < k){
            l = i + 1;
            continue;
        } 
        if(x > n) break;
        f[i] = suujikonn(x);
        cnt[f[i]]++;
        while(cnt[f[i]] > 1){
            cnt[f[l]]--;
            l++;
        }
        if(i-l+1>=ma){
            ma = i-l+1;
            ans = primes[l];
        }
    }

    cout << ans << endl;
    return 0;
}