#include <algorithm>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <vector>
#define rep(i, n) for (int i = 0; i < (n); i++)
#define rrep(i, n) for (int i = (n)-1; i >= 0; i--)
using namespace std;
typedef long long int lli;
lli MOD = 1000000007;
vector<int> prime(int n, int k)
{
    bool isprime[2000005] = {};
    vector<int> primes;
    for (int i = 2; i <= n; i++) {
        if (!isprime[i]) {
            if (i >= k)
                primes.push_back(i);
            for (int j = 2 * i; j <= n; j += i) {
                isprime[j] = true;
            }
        }
    }
    return primes;
}
int memo[200005] = {};
int h(int g)
{
    int t = g;
    if (memo[g])
        return memo[g];
    int sum = 0;
    while (g > 0) {
        sum += g % 10;
        g /= 10;
    }
    if (sum < 10)
        return memo[t] = sum;
    else
        return memo[t] = h(sum);
}
int main()
{
    int k, n;
    cin >> k >> n;
    vector<int> p = prime(n, k);
    int ans = 0;
    int aa = 0;
    for (int i = 0; i < p.size(); i++) {
        set<int> u;
        for (int j = i; j < p.size(); j++) {
            //cout << p[j] << '(' << h(p[j]) << ' ';
            if (u.find(h(p[j])) != u.end()) {
                if (ans <= j - i - 1) {
                    ans = max(ans, j - i - 1);
                    aa = p[i];
                }
                break;
            } else {
                u.insert(h(p[j]));
            }
            if (j == (int)p.size() - 1) {
                if (ans <= j - i) {
                    ans = max(ans, j - i);
                    aa = p[i];
                }
            }
        }
        //    cout << endl;
    }
    cout << aa << endl;
}