using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (n, k) = (c[0], c[1]);
        var plist = GetMinPDivList(n);
        var nc = 1;
        var np = PDiv(n, plist);
        {
            foreach (var kv in np) nc *= kv.Value + 1;
        }
        var ans = 0;
        var ansc = 0;
        for (var i = 1; i < n; ++i)
        {
            var p = PDiv(i, plist);
            var count = 0;
            var pcount = 1;
            foreach (var kv in p)
            {
                if (np.ContainsKey(kv.Key)) count += Math.Min(np[kv.Key], kv.Value);
                pcount *= kv.Value + 1;
            }
            if (count >= k && ansc < pcount)
            {
                ans = i;
                ansc = pcount;
            }
        }
        WriteLine(ans);
    }
    static int[] GetMinPDivList(int max)
    {
        var minPDivList = new int[max + 1];
        for (var i = 0; i <= max; ++i) minPDivList[i] = i;

        for (var i = 2; i * i <= max; ++i) if (minPDivList[i] == i)
        {
            for (var j = i * i; j <= max; j += i) if (minPDivList[j] == j)
            {
                minPDivList[j] = i;
            }
        }
        return minPDivList;
    }
    static Dictionary<int, int> PDiv(int n, int[] minPDivList)
    {
        var p = minPDivList[n];
        if (n == p)
        {
            var dic = new Dictionary<int, int>();
            if (dic.ContainsKey(p)) ++dic[p];
            else dic[p] = 1;
            return dic;
        }
        else
        {
            var dic = PDiv(n / p, minPDivList);
            if (dic.ContainsKey(p)) ++dic[p];
            else dic[p] = 1;
            return dic;
        }
    }
}