#include<bits/stdc++.h>
using namespace std;
#define INF 0x3f3f3f3f
#define PI acos(-1)
#define io ios::sync_with_stdio(false); cin.tie(0); cout.tie(0)
#define mem(a,b) memset((a),(b),sizeof(a))
typedef long long ll;
typedef unsigned long long ull;
#define int long long
#define db long double

const double eps = 1e-6;
const int mod = 1e9 + 7;
const int maxn = 1e5 + 10;

int n;

void solve() {
    cin >> n;
    if (n % 3 == 0) {
        cout << n * n * n / 27 << '\n';
    } else if (n % 4 == 0) {
        cout << n * n * n / 4 / 4 / 2 << '\n';
    } else {
        cout << "-1\n";
    }
}

signed main(){
    io;
    int T = 1;
    cin >> T;
    while(T--) {
        solve();
    }
    return 0;
}