using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

class Magatro
{
    static int N, K;
    static List<int> Prime = new List<int>(),hash=new List<int>();
    static bool[] flag = new bool[10];
    static void Main()
    {
        Read();
        Primecnt();
        Hashcalc();
        int migi = 0;
        int hidari = 0;
        int max=0;
        int first = 0;
        for (int i = 0; i < Prime.Count; i++)
        {
            if (!flag[hash[i]])
            {
                migi++;
                flag[hash[i]] = true;
            }
            else
            {

                if (migi - hidari + 1 >= max) {
                    max = migi - hidari + 1;
                    first = hidari;
                }
                for (int j = hidari; hash[i] != hash[j]; j++)
                {
                    hidari++;
                    flag[hash[j]] = false;
                }
                hidari++;
                migi++;
                //   flag[hash[i]] = false;
            }
        }
        if (migi - hidari + 1 >= max)
        {
            max = migi - hidari + 1;
            first = hidari;
        }
        Console.WriteLine(Prime[first]);
    }
    static void Hashcalc()
    {
        for(int i = 0; i <Prime.Count; i++)
        {
            hash.Add(calc(calc(calc((Prime[i])))));
        }
    }
    static int calc(int n)
    {
        if (n<10)
        {
            return n;
        }
        return calc(n / 10) + n % 10;
    }
    static void Primecnt()
    {
        bool[] n = (new bool[N + 1]).Select(s => true).ToArray();
        n[0] = false;
        n[1] = false;
        int rootN = (int)Math.Sqrt(N) + 1;
        for (int i = 2; i <= rootN; i++)
        {
            if (n[i])
            {
                for (int j = i + i; j <= N; j += i)
                {
                    n[j] = false;
                }
            }
        }
        for (int i = K; i <= N; i++)
        {
            if (n[i])
            {
                Prime.Add(i);
            }
        }
    }
    static void Read()
    {
        K = int.Parse(Console.ReadLine());
        N = int.Parse(Console.ReadLine());
    }

}