using static System.Math;
using System;

public class Hello
{
    static void Main()
    {
        var x = long.Parse(Console.ReadLine().Trim());
        getAns(x);
    }
    static void getAns(long x)
    {
        var imin = Max(0, x - 60);
        var imax = x + 60;
        for (long i = imin; i <= imax; i++)
        {
            if ((i ^ cb(i)) == x) { Console.WriteLine(i); return; }
        }
        Console.WriteLine(-1);
    }
    static int cb(long bits)
    {
        bits = (bits & 0x55555555) + (bits >> 1 & 0x55555555);
        bits = (bits & 0x33333333) + (bits >> 2 & 0x33333333);
        bits = (bits & 0x0f0f0f0f) + (bits >> 4 & 0x0f0f0f0f);
        bits = (bits & 0x00ff00ff) + (bits >> 8 & 0x00ff00ff);
        return (int)(bits & 0x0000ffff) + (int)(bits >> 16 & 0x0000ffff);
    }
}