#include <bits/stdc++.h>

using namespace std;

#define REP(i, n)   for(int i = 0; i < (n); i++)
#define REPS(i, n)  for(int i = 1; i <= (n); i++)
#define RREP(i, n)  for(int i = (n)-1; i >= 0; i--)
#define RREPS(i, n) for(int i = (n); i > 0; i--)
#define ALL(v) v.begin(), v.end()
#define RALL(v) v.rbegin(), v.rend()
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define mp make_pair
#define mt make_tuple
#define pb push_back

using ll  = long long;
using pi  = pair<int, int>;
using pl  = pair<ll, ll>;
using vi  = vector<int>;
using vl  = vector<ll>;
using vs  = vector<string>;
using vvi = vector<vi>;

const int MOD = 1e9 + 7;
const int INF = 1e9 + 7;

template<class T> bool chmax(T &a, const T &b) { if(a < b) { a = b; return true; } return false; }
template<class T> bool chmin(T &a, const T &b) { if(a > b) { a = b; return true; } return false; }

int h(int n)
{
    int ret = 0;
    while(n > 0)
    {
        ret += n % 10;
        n /= 10;
    }
    if(ret < 10) return ret;
    return h(ret);
}

int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);

    int K, N; cin >> K >> N;
    vector<bool> isPrime(N+1, true);
    isPrime[0] = isPrime[1] = false;
    for(int i = 2; i * i <= N; i++)
    {
        if(isPrime[i])
        {
            for(int j = i*2; j <= N; j+=i) isPrime[j] = false;
        }
    }

    vi a, b;
    REPS(i, N) if(isPrime[i] && i >= K) a.push_back(i), b.push_back(h(i));

/*
    while(left < l && right < l)
    {
        while(right < l && s.find(b[right]) == s.end())
        {
            s.insert(b[right]);
            right++;
        }
        if(m <= right - left)
        {
            m = right - left;
            idx = left;
        }
        while(left < l && b[left] != b[right])
        {
            s.erase(b[left]);
            left++;
        }
        s.erase(b[left]);
    }
    cout << m << endl;
    cout << a[idx] << endl;
*/

    int l = (int)a.size();
    int m = 0, idx = 0;

    for(int left = 0; left < l; left++)
    {
        set<int> s;
        int right = left;
        while(right < l && s.find(b[right]) == s.end())
        {
            s.insert(b[right]);
            right++;
        }
        if(right - left >= m)
        {
            m = right - left;
            idx = left;
        }
    }
    cout << a[idx] << endl;
}