// AYASHII 

#include <bits/stdc++.h>
using ll = long long;

const ll width = 1001001;

ll isqrt(ll n){
    if (n == 0) return 0;
    ll x = std::sqrt(n) - 1;
    return (x * (x + 2) < n ? x + 1 : x);
}

void solve(){
    ll n; std::cin >> n;
    ll sq = isqrt(n);
    for (ll s = sq - width; s <= sq + width; s++){
        if (s < 0) continue;
        ll k = n ^ s;
        if (s*s <= k && k < (s+1)*(s+1)){
            std::cout << k << '\n';
            return ;
        }
    }
    std::cout << -1 << '\n';
}

int main(){
    int t; std::cin >> t;
    while (t--){
        solve();
    }
}