#include <iostream>
#define int long long
using namespace std;

signed main() {
	int T;
	cin >> T;
	while (T--) {
		int n;
		cin >> n;

		int ok = 0, ng = (1LL << 30), mid;
		while (ng - ok >= 2) {
			mid = (ok + ng) / 2;
			if (mid * mid <= n) ok = mid;
			else ng = mid;
		}

		int sqK = ok;
		int k = n ^ sqK;
		if (sqK * sqK <= k && k < (sqK + 1) * (sqK + 1)) {
			cout << k << endl;
		}
		else {
			cout << -1 << endl;
		}
	}
	return 0;
}