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();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var x = long.Parse(ReadLine());
        for (var i = 1; i < 64; ++i)
        {
            var n = x ^ i;
            if (Weight(n) == i)
            {
                WriteLine(n);
                return;
            }
        }
        WriteLine(-1);
    }
    static int Weight(long n)
    {
        var ans = 0;
        while (n > 0)
        {
            ans += (int)(n % 2);
            n >>= 1;
        }
        return ans;
    }
}