#define _CRT_SECURE_NO_DEPRECATE
#include <stdio.h>
#include <iostream>
#include <string>
#include <string.h>
#include <vector>
#include <set>
#include <map>
#include <memory.h>
#include <algorithm>
#include <math.h>
#include <queue>
using namespace std;
typedef long long li;
typedef long double ld;
#define mp make_pair
#define pb push_back
typedef pair <li, li> pi;
typedef vector <li, li> vli;
typedef vector <int> vi;
void solve ();
int main ()
{
#ifdef _DEBUG
        freopen ("in.txt", "r", stdin);
        //freopen ("out.txt", "w", stdout);
#endif
        int t=1;
        while (t--)
        solve ();
}
#define int li
int n;
int kuda;
int gr[100500];
int doing ( int k )
{
        if ( gr[k]!=-1 )
                return gr[k];
        int now=2*k;
        vector <int> del;
        for ( int i=2; i*i<=now; i++ )
                if ( now%i==0 )
                {
                        del.pb (i);
                        if ( i*i!=now )
                                del.pb (now/i);
                }
        sort (del.begin(), del.end());
        int num=0;
        int ans=0;
        for ( int i=0; i<del.size(); i++ )
        {
                int curans=1;
                int h=now/del[i];
                if ( h>=del[i]+1 && (h-del[i]-1)%2==0 )
                {
                        int z=h-del[i]-1; z/=2;
                        if (k==n)
                        cout<<z<<' '<<del[i]<<endl;
                        for ( int j=1; j<=del[i]; j++ )
                        {
                                int cur=doing(z+j);
                                        curans^=cur;
                                //cout<<z+j<<' '<<cur<<endl;
                        }
                        if ( curans>ans )
                        {
                                ans=curans;
                                //cout<<k<<' '<<curans<<endl;
                                num=del[i];
                                break;
                        }
                }
        }
        gr[k]=ans;
        if ( k==n && ans==1 )
                kuda=num;
        return ans;
}
void solve ()
{
        cin>>n;
        memset (gr, -1, sizeof (gr));
        for ( int i=1; i<=n; i=i<<1 )
                gr[i]=0;
        int answer=doing (n);
        if ( answer )
                cout<<kuda;
        else
                cout<<"-1";
}