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

class Program
{
    static void Main(string[] args)
    {
        new Program().Calc();
    }

    Scanner cin;

    public Program() { }

    bool chmax<T>(ref T a, T b) where T : IComparable<T> { if (a.CompareTo(b) < 0) { a = b; return true; } return false; }
    bool chmin<T>(ref T a, T b) where T : IComparable<T> { if (b.CompareTo(a) < 0) { a = b; return true; } return false; }

    void Calc()
    {
        cin = new Scanner();

        long A = cin.nextLong();
        long B = cin.nextLong();

        long ans = 0;

        if (B == 0)
        {
            ans = 0;
        }
        else if (A == 0)
        {
            ans = TotalXOR(B);
        }
        else
        {
            ans = TotalXOR(B) ^ TotalXOR(A - 1);
        }

        WriteLine(ans);

#if false

        WriteLine(TotalXOR(14));
        WriteLine(TotalXOR_Perfect(14));

        WriteLine(TotalXOR(122));
        WriteLine(TotalXOR_Perfect(122));

        WriteLine(TotalXOR(436));
        WriteLine(TotalXOR_Perfect(436));

        for (int i = 0; i < 30; ++i)
        {
            WriteLine("{0} {1}", TotalXOR_Perfect(i * 4 + 2), i * 4 + 3);
        }

        WriteLine(Convert.ToString(456, 2).PadLeft(12, '0'));
        WriteLine(Convert.ToString(122, 2).PadLeft(12, '0'));
        WriteLine(Convert.ToString(435, 2).PadLeft(12, '0'));
        WriteLine(Convert.ToString(123, 2).PadLeft(12, '0'));
#endif
    }

    long TotalXOR(long num)
    {
        switch (num % 4)
        {
            case 0:
                return num;
            case 1:
                return 1;
            case 2:
                return num / 4 * 4 + 3;
            case 3:
            default:
                return 0;
        }
    }

    long TotalXOR_Perfect(long num)
    {
        long ans = 0;

        for (int i = 1; i <= num; ++i)
        {
            ans ^= i;
        }

        return ans;
    }
}

public static class StringExtension
{
    public static char GetChar1(this string str, int indexOneBase)
    {
        return str[indexOneBase - 1];
    }
}

class Scanner
{
    string[] s;
    int i;

    char[] cs = new char[] { ' ' };

    public Scanner()
    {
        s = new string[0];
        i = 0;
    }

    public string next()
    {
        if (i < s.Length) return s[i++];
        string st = Console.ReadLine();
        while (st == "") st = Console.ReadLine();
        s = st.Split(cs, StringSplitOptions.RemoveEmptyEntries);
        if (s.Length == 0) return next();
        i = 0;
        return s[i++];
    }

    public int nextInt()
    {
        return int.Parse(next());
    }
    public int[] ArrayInt(int N, int add = 0)
    {
        int[] Array = new int[N];
        for (int i = 0; i < N; i++)
        {
            Array[i] = nextInt() + add;
        }
        return Array;
    }

    public long nextLong()
    {
        return long.Parse(next());
    }

    public long[] ArrayLong(int N, long add = 0)
    {
        long[] Array = new long[N];
        for (int i = 0; i < N; i++)
        {
            Array[i] = nextLong() + add;
        }
        return Array;
    }

    public double nextDouble()
    {
        return double.Parse(next());
    }


    public double[] ArrayDouble(int N, double add = 0)
    {
        double[] Array = new double[N];
        for (int i = 0; i < N; i++)
        {
            Array[i] = nextDouble() + add;
        }
        return Array;
    }
}


Measured memory_bytes: 13140