#line 1 "main.cpp"
#include <iostream>

using namespace std;
using lint = long long;

void solve() {
    lint x;
    cin >> x;

    for (int b = 1; b <= 62; ++b) {
        auto y = (x ^ b);
        if (__builtin_popcountll(y) == b) {
            cout << y << "\n";
            return;
        }
    }

    cout << "-1\n";
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    solve();

    return 0;
}