#include <iostream>
#include <string>
#include <queue>
#include <stack>
#include <algorithm>
#include <list>
#include <vector>
#include <complex>
#include <utility>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <bitset>
#include <ctime>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <cassert>
#include <cstddef>
#include <iomanip>
#include <numeric>
#include <tuple>
#include <sstream>
#include <fstream>
#include <random>

#define REP(i, n) for (int (i) = 0; (i) < (n); (i)++)
#define FOR(i, a, b) for (int (i) = (a); (i) < (b); (i)++)
#define RREP(i, a) for(int (i) = (a)-1; (i) >= 0; (i)--)
#define FORR(i, a, b) for(int (i) = (a)-1; (i) >= (b); (i)--)
#define PI acos(-1.0)
#define DEBUG(C) cerr << C << endl;
#define VI vector <int>
#define VII vector <VI>
#define VL vector <LL>
#define VLL vector <VL>
#define VD vector <double>
#define VDD vector <VD>
#define PII pair <int, int>
#define PDD pair <double, double>
#define PLL pair <LL, LL>
#define VPII vector <PII>
#define ALL(a) (a).begin(), (a).end()
#define SORT(a) sort(ALL(a))
#define REVERSE(a) reverse(ALL(a))
#define MP make_pair
#define EB emplace_back
#define FORE(a, b) for (auto &&a : b)
#define FIND(s, n) (s.find(n) != s.end())

using namespace std;
typedef long long LL;
typedef unsigned long long ULL;
const int INF = 1e9;
const int MOD = INF + 7;
const LL LLINF = 1e18;

int K, N;
int hs[200010];

vector <int> sieve_of_eratosthenes(int n) {
    vector <bool> is(n+1, true);
    vector <int> res;
    is[0] = false;
    is[1] = false;
    for (int i = 2; i <= n; i++) {
        if (is[i]) {
            res.emplace_back(i);
            for (int j = i*2; j <= n; j+=i) {
                is[j] = false;
            }
        }
    }
    return res;
}

int makeHash(int num) {
    if (num < 10) return num;
    int res = 0;
    while (num) {
        res += num % 10;
        num /= 10;
    }
    return makeHash(res);
}
void out(vector <PII> v) {
    FORE(el, v) cout << el.first << " " << el.second << endl;
}
int main(void) {
    cin >> K >> N;
    REP(i, 200010) hs[i] = makeHash(i);
    PII ans = MP(0, 0);
    int maxsize = 0;
    set <int> hsset;
    auto primes = sieve_of_eratosthenes(N + 10);
    vector <PII> v;
    FORE(el, primes) {
        if (el < K) continue;
        if (N < el) break;
        v.EB(MP(el, hs[el]));
    }
    int j = 0;
    //out(v);
    REP(i, v.size()) {
        while (true) {
            if (j >= v.size()) break;
            if (FIND(hsset, v[j].second)) {
                break;
            } else {
                hsset.insert(v[j++].second);
            }
        }
        if (maxsize <= hsset.size()) {
            maxsize = hsset.size();
            ans = MP(v[i].first, v[j].first);
        }
        hsset.erase(v[i].second);
    }
    //cerr << ans.first << " " << ans.second << " " << maxsize << endl;
    cout << ans .first << endl;
    return 0;
}