#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for(ll i = 0, i##_len = (n); i < i##_len; i++)
#define reps(i, s, n) for(ll i = (s), i##_len = (n); i < i##_len; i++)
#define rrep(i, n) for(ll i = (n) - 1; i >= 0; i--)
#define rreps(i, e, n) for(ll i = (n) - 1; i >= (e); i--)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) ((ll)(x).size())
#define len(x) ((ll)(x).length())
#define endl "\n"

struct isPrime {
private:
    vector<bool> data;
    
public:
    isPrime() {}
    isPrime(int n) {
        data.resize(n + 1, true);
        data[0] = data[1] = false;
        for(long long i = 2; (i * i) <= n; i++) {
            if (!data[i]) continue;
            for(long long j = 2; (i * j) <= n; j++) {
                data[i * j] = false;
            }
        }
    }
    
    bool is_prime(int n) {
        return data[n];
    }
    
    vector<int> get_primes_vector() {
        vector<int> ans;
        int n = data.size();
        for(int i = 0; i < n; i++) {
            if (data[i]) ans.push_back(i);
        }
        return ans;
    }
    
    set<int> get_primes_set() {
        set<int> ans;
        int n = data.size();
        for(int i = 0; i < n; i++) {
            if (data[i]) ans.insert(i);
        }
        return ans;
    }
};

ll get_hash(ll n) {
    while(n >= 10) {
        ll tmp = 0;
        while(n > 0) {
            tmp += n % 10;
            n /= 10;
        }
        n = tmp;
    }
    return n;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    // ifstream in("input.txt");
    // cin.rdbuf(in.rdbuf());
    ll k, n;
    cin >> k >> n;
    isPrime ip(n);
    auto pv = ip.get_primes_vector();
    auto it = lower_bound(all(pv), k);
    ll l = (it - pv.begin()) - 1;
    ll r = l;
    set<ll> s;
    ll mcnt = 1, mval = pv[l];
    while(l < sz(pv)) {
        if (l >= 0) {
            s.erase(get_hash(pv[l]));
        }
        l++;
        while((r + 1) < sz(pv)) {
            ll v = get_hash(pv[r + 1]);
            if (s.count(v) > 0) break;
            s.insert(v);
            r++;
        }
        if ((r - l) >= mcnt) {
            mcnt = r - l;
            mval = pv[l];
        }
    }
    cout << mval << endl;
    return 0;
}