using System;
using System.Linq;
using System.Diagnostics;
using System.Collections.Generic;
using Debug = System.Diagnostics.Debug;
using StringBuilder = System.Text.StringBuilder;
using System.Numerics;
using Number = System.Int64;
using Point = System.Numerics.Complex;
namespace Program
{
    public class Solver
    {
        public void Solve()
        {
            var l = sc.Long();
            var h = sc.Long();
            var primes = MathEx.SieveList(100050);
            if (h - l <= 20000)
            {
                var ans = -1L;
                var otaku = -1L;
                for (long i = l; i <= h; i++)
                {
                    var x = i;
                    var min = 10000000000;
                    var cnt = 0;
                    foreach (var v in primes)
                    {
                        while (x % v == 0)
                        {
                            min = Math.Min(min, v);
                            x /= v;
                            cnt++;
                            break;
                        }
                    }
                    if (x > 1) { cnt++; min = Math.Min(min, x); }
                    if (cnt > 1)
                    {
                        if (otaku < min)
                        {
                            otaku = min;
                            ans = i;
                        }
                        else if (otaku == min)
                        {
                            ans = Math.Max(ans, i);
                        }
                    }
                }
                IO.Printer.Out.WriteLine(ans);
                return;
            }
            {
                var n = primes.Count;
                var ans = -1L;
                for (int i = n - 1; i >= 0; i--)
                {
                    var p = primes[i];
                    var q = new Queue<long>();
                    q.Enqueue(p);
                    var set = new HashSet<long>();
                    while (q.Any())
                    {
                        var v = q.Dequeue();
                        if (p != v && l <= v) ans = Math.Max(ans, v);
                        for (int j = i; j < n; j++)
                        {
                            var next = v * primes[j];
                            if (next > h) break;
                            if (set.Add(next))
                                q.Enqueue(next);
                        }
                    }
                    if (ans != -1)
                    {
                        IO.Printer.Out.WriteLine(ans);
                        return;
                    }
                }
            }
        }

        public IO.StreamScanner sc = new IO.StreamScanner(Console.OpenStandardInput());
        static T[] Enumerate<T>(int n, Func<int, T> f) { var a = new T[n]; for (int i = 0; i < n; ++i) a[i] = f(i); return a; }
        static public void Swap<T>(ref T a, ref T b) { var tmp = a; a = b; b = tmp; }
    }
}

#region main
static class Ex
{
    static public string AsString(this IEnumerable<char> ie) { return new string(System.Linq.Enumerable.ToArray(ie)); }
    static public string AsJoinedString<T>(this IEnumerable<T> ie, string st = " ") { return string.Join(st, ie); }
    static public void Main()
    {
        var solver = new Program.Solver();
        solver.Solve();
        Program.IO.Printer.Out.Flush();
    }
}
#endregion
#region Ex
namespace Program.IO
{
    using System.IO;
    using System.Text;
    using System.Globalization;
    public class Printer : StreamWriter
    {
        static Printer() { Out = new Printer(Console.OpenStandardOutput()) { AutoFlush = false }; }
        public static Printer Out { get; set; }
        public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } }
        public Printer(System.IO.Stream stream) : base(stream, new UTF8Encoding(false, true)) { }
        public Printer(System.IO.Stream stream, Encoding encoding) : base(stream, encoding) { }
        public void Write<T>(string format, T[] source) { base.Write(format, source.OfType<object>().ToArray()); }
        public void WriteLine<T>(string format, T[] source) { base.WriteLine(format, source.OfType<object>().ToArray()); }
    }
    public class StreamScanner
    {
        public StreamScanner(Stream stream) { str = stream; }
        public readonly Stream str;
        private readonly byte[] buf = new byte[1024];
        private int len, ptr;
        public bool isEof = false;
        public bool IsEndOfStream { get { return isEof; } }
        private byte read()
        {
            if (isEof) return 0;
            if (ptr >= len) { ptr = 0; if ((len = str.Read(buf, 0, 1024)) <= 0) { isEof = true; return 0; } }
            return buf[ptr++];
        }
        public char Char() { byte b = 0; do b = read(); while ((b < 33 || 126 < b) && !isEof); return (char)b; }

        public string Scan()
        {
            var sb = new StringBuilder();
            for (var b = Char(); b >= 33 && b <= 126; b = (char)read())
                sb.Append(b);
            return sb.ToString();
        }
        public string ScanLine()
        {
            var sb = new StringBuilder();
            for (var b = Char(); b != '\n'; b = (char)read())
                if (b == 0) break;
                else if (b != '\r') sb.Append(b);
            return sb.ToString();
        }
        public long Long()
        {
            if (isEof) return long.MinValue;
            long ret = 0; byte b = 0; var ng = false;
            do b = read();
            while (b != 0 && b != '-' && (b < '0' || '9' < b));
            if (b == 0) return long.MinValue;
            if (b == '-') { ng = true; b = read(); }
            for (; true; b = read())
            {
                if (b < '0' || '9' < b)
                    return ng ? -ret : ret;
                else ret = ret * 10 + b - '0';
            }
        }
        public int Integer() { return (isEof) ? int.MinValue : (int)Long(); }
        public double Double() { var s = Scan(); return s != "" ? double.Parse(s, CultureInfo.InvariantCulture) : double.NaN; }
        private T[] enumerate<T>(int n, Func<T> f)
        {
            var a = new T[n];
            for (int i = 0; i < n; ++i) a[i] = f();
            return a;
        }

        public char[] Char(int n) { return enumerate(n, Char); }
        public string[] Scan(int n) { return enumerate(n, Scan); }
        public double[] Double(int n) { return enumerate(n, Double); }
        public int[] Integer(int n) { return enumerate(n, Integer); }
        public long[] Long(int n) { return enumerate(n, Long); }
    }
}
#endregion
#region sieve list
static public partial class MathEx
{
    static public List<int> SieveList(int p)
    {
        var isPrime = new bool[p + 1];
        for (int i = 2; i <= p; i++)
            isPrime[i] = true;
        for (int i = 2; i * i <= p; i++)
        {
            if (!isPrime[i])
                continue;
            for (int j = i * i; j <= p; j += i)
                isPrime[j] = false;
        }
        var ret = new List<int>();
        for (int i = 0; i <= p; i++) if (isPrime[i]) ret.Add(i);
        return ret;
    }
}
#endregion
#region Compair
static public class Pair
{
    static public Pair<FT, ST> Create<FT, ST>(FT f, ST s)
        where FT : IComparable<FT>
        where ST : IComparable<ST>
    { return new Pair<FT, ST>(f, s); }
    static public Pair<FT, ST> Min<FT, ST>(Pair<FT, ST> p, Pair<FT, ST> q)
        where FT : IComparable<FT>
        where ST : IComparable<ST>
    { return (p.CompareTo(q) <= 0) ? p : q; }
    static public Pair<FT, ST> Max<FT, ST>(Pair<FT, ST> p, Pair<FT, ST> q)
        where FT : IComparable<FT>
        where ST : IComparable<ST>
    { return (p.CompareTo(q) >= 0) ? p : q; }
}
public struct Pair<FT, ST> : IComparable<Pair<FT, ST>>
    where FT : IComparable<FT>
    where ST : IComparable<ST>
{
    public FT x;
    public ST y;
    public Pair(FT f, ST s) : this() { x = f; y = s; }

    public int CompareTo(Pair<FT, ST> other)
    {
        var cmp = x.CompareTo(other.x);
        return cmp != 0 ? cmp : y.CompareTo(other.y);
    }
    public override string ToString() { return string.Format("{0} {1}", x, y); }
}
#endregion