#include <algorithm>
#include <cmath>
#include <cstring>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <iterator>

#define pb push_back
#define puts(x) cout << #x << " : " << x << endl;
#pragma GCC diagnostic ignored "-Wconversion"

#define REP(i,n) for (int i=0;i<(n);i++)
#define REPE(i,n) for (int i=0;i<=(n);i++)

#define init(a,b) memset((a), (b), (sizeof(a)));

#define PI 3.14159265
#define EPS (1e-10)
#define EQ(a,b) (abs((a)-(b)) < EPS)

using namespace std;

typedef long long ll;
typedef pair<int, int> P;

vector<bool> prime_table(1000*1000);
set<int> prime_set;
vector<int> primes;
void make_primes() {
    fill(prime_table.begin(), prime_table.end(), 1);
    prime_table[0] = prime_table[1] = 0;
    for (int i = 2; i < 1000*1000; i++) {
        if (prime_table[i]) {
            prime_set.insert(i);
            primes.push_back(i);
            for (int j = i * 2; j < 1000*1000; j += i) {
                prime_table[j] = 0;
            }
        }
    }
}

int hsh(int t){
    while(t >= 10){
        stringstream ss;
        ss<<t;
        string s = ss.str();
        t=0;
        for(int i = 0;i<s.size();i++){
            t += (int)(s[i]-'0');
        }
    }
    return t;
}

vector<int> hash_list;
map<int, int> mp;

int main() {
    make_primes();
    int K,N;cin>>K>>N;

    for(int i=0;i<primes.size();i++){
        if(K<=primes[i]&&primes[i]<=N){
            mp[hash_list.size()] = primes[i];
            hash_list.push_back(hsh(primes[i]));
        }
    }

    int res = 0, res2 = 0;
    bool used[10];
    for(int i=0;i<hash_list.size();i++){
        int cnt=0;
        memset(used, 0, sizeof(used));
        for(int j=i;j<hash_list.size();j++){
            if(used[hash_list[j]])break;
            cnt++;
            used[hash_list[j]]=1;
        }
        if(res<=cnt){
            res2 = mp[i];
            res=cnt;
        }
    }

    cout<<res2<<endl;

    return 0;
}