#include<bits/stdc++.h>
using namespace std;
#define ALL(x) begin(x),end(x)
#define rep(i,n) for(int i=0;i<(n);i++)
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define mod 1000000007
using ll=long long;
const int INF=1000000000;
const ll LINF=1001002003004005006ll;
int dx[]={1,0,-1,0},dy[]={0,1,0,-1};
// ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return true;}return false;}

struct IOSetup{
    IOSetup(){
        cin.tie(0);
        ios::sync_with_stdio(0);
        cout<<fixed<<setprecision(12);
    }
} iosetup;
 
template<typename T>
ostream &operator<<(ostream &os,const vector<T>&v){
    for(int i=0;i<(int)v.size();i++) os<<v[i]<<(i+1==(int)v.size()?"":" ");
    return os;
}
template<typename T>
istream &operator>>(istream &is,vector<T>&v){
    for(T &x:v)is>>x;
    return is;
}

// 2^127 = 170141183460469231731687303715884105728 ~ 10^38
 
ostream &operator<<(ostream &os,const __int128 &n){
    if(n==0){
        os<<0;
        return os;
    }
    __int128 num=n;
    bool neg=false;
    if(num<0)neg=true,num=-num;
    string res="";
    while(num>0){
        res.push_back('0'+num%10);
        num/=10;
    }
    if(neg) res.push_back('-');
    reverse(begin(res),end(res));
    os<<res;
    return os;
}

istream &operator>>(istream &is,__int128 &n){
    string s;
    is>>s;
    int idx=0;
    bool neg=false;
    if(s[0]=='-')neg=true,idx++;
    n=0;
    for(;idx<(int)s.size();idx++){
        n=10*n+s[idx]-'0';
    }
    if(neg) n=-n;
    return is;
}

__int128 abs128(__int128 x){
    return x<0?-x:x;
}
 
__int128 gcd128(__int128 a,__int128 b){
    if(a==0) return b;
    if(b==0) return a;
    return b>0?gcd128(b,a%b):a;
}
using int128=__int128;

signed main(){
    ll x;cin>>x;
    for(ll i=0;i<63;i++){
        // i : popcount
        ll rem=(x^i);
        if(__builtin_popcount(rem)==i){
            cout<<rem<<endl;
            return 0;
        }
    }
    
    cout<<-1<<endl;
    return 0;
}