#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (ll i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("YES");}else{puts("NO");}
#define MAX_N 200005

int main() {
    ll x; cin >> x;
    ll ans = -1;
    rep(i,100){
        ll n = x ^ i;
        if(__builtin_popcountll(n) == i){
            // cout << n << endl;
            ans = n;
        }
    }
    cout << ans << endl;
    return 0;
}