#include <iostream>
#include <sstream>
#include <math.h>
#include <vector>
#include <array>
#include <algorithm>
#include <queue>
#include <numeric>
#include <map>
#include <set>
#include <bitset>

using namespace std;
#define int long long
#define FOR(i, a, b) for(int i=(a);i<(b);i++)
#define RFOR(i, a, b) for(int i=(b-1);i>=(a);i--)
#define REP(i, n) for(int i=0; i<(n); i++)
#define RREP(i, n) for(int i=(n-1); i>=0; i--)
#define ALL(a) (a).begin(),(a).end()
#define UNIQUE_SORT(l) sort(ALL(l)); l.erase(unique(ALL(l)), l.end());
#define CONTAIN(a, b) find(ALL(a), (b)) != (a).end()
#define SUM(a) accumulate(ALL(a), 0)
#define array2(type, x, y) array<array<type, y>, x>
#define vector2(type) vector<vector<type> >
#define out(...) printf(__VA_ARGS__)

typedef pair<int, int> pos;
int pos::*x = &pos::first;
int pos::*y = &pos::second;

int dxy[] = {0, 1, 0, -1, 0};

/*================================*/
int N, K;
bool furui[200100];
map<int, int> hash1;

int getHash(int n) {
    while (n >= 10) {
        int s = 0;
        while (n > 0) {
            s += n % 10;
            n /= 10;
        }
        n = s;
    }
    return n;
}

signed main()
{
    vector<int> primes;
    cin >> K >> N;
    furui[0] = furui[1] = true;
    FOR(i,2,N+1) {
        if (furui[i] == false) {
            primes.push_back(i);
            hash1[i] = getHash(i);
            int k = 2;
            while(i*k < N+1) {
                furui[i*k] = true;
                k++;
            }
        }
    }
    
    int maxlen = 0;
    int maxleni = -1;
    int tmplen = 0;
    int tmpleni = -1;
    set<int> hashes;
    REP(i,primes.size()) {
        if (primes[i] < K) continue;
        int h = hash1[primes[i]];
        if (hashes.find(h) != hashes.end()) {
            if (maxlen <= tmplen) {
                maxlen = tmplen;
                maxleni = tmpleni;
            }
            i = tmpleni; // ループを戻す
            hashes = set<int>();
            tmplen = 0;
            tmpleni = -1;
        } else {
            hashes.insert(h);
            tmplen++;
            if (tmpleni == -1) tmpleni = i;
        }
    }
    if (maxlen <= tmplen) {
        maxlen = tmplen;
        maxleni = tmpleni;
    }
    
    cout << primes[maxleni] << endl;
    
    return 0;
}