#include<bits/stdc++.h>
using namespace std;
//#pragma GCC optimize("Ofast")

#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=(n)-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x,vector<x>,greater<x>>
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define vtpl(x,y,z) vector<tuple<x,y,z>>
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=1e9+10;
const ll INF=4e18;
//const ll dy[9]={1,0,-1,0,1,1,-1,-1,0};
//const ll dx[9]={0,1,0,-1,1,-1,1,-1,0};
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

void solve(){
    ll n;cin >> n;
    string s=to_string(n);
    if(s.size()<=6){
        rep(i,1000000){
            ll p=sqrtl(i);
            if((i^p)==n){
                cout << i << endl;return;
            }
        }
        cout << -1 << endl;return;
    }
    ll t=s.size()/2;
    string l,r;
    rep(_,t)l+=s[_],r+=s[_];
    rep(_,s.size()-t)l+='0';
    ll lx=stoll(l);
    rep(_,s.size()-t)r+='9';
    ll rx=stoll(r);
    lx=sqrtl(lx);
    rx=sqrtl(rx);
    for(ll p=lx;p<=rx;p++){
        ll to=p^n;
        if(p*p<=to&&to<(p+1)*(p+1)){
            cout << to << endl;return;
        }
    }
    cout << -1 << endl;return;


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

}