// Hallelujah, praise the one who set me free
// Hallelujah, death has lost its grip on me
// You have broken every chain, There's salvation in your name
// Jesus Christ, my living hope
#include <bits/stdc++.h> 
using namespace std;

#define REP(i, s, e) for (int i = (s); i < (e); i++)
#define RREP(i, s, e) for (int i = (s); i >= (e); i--)
template <class T>
inline bool mnto(T& a, T b) {return a > b ? a = b, 1 : 0;}
template <class T>
inline bool mxto(T& a, T b) {return a < b ? a = b, 1: 0;}
typedef long long ll;
typedef long double ld;
#define FI first
#define SE second
typedef pair<int, int> ii;
typedef pair<ll, ll> pll;
typedef tuple<int, int, int> iii;
#define ALL(_a) _a.begin(), _a.end()
#define SZ(_a) (int) _a.size()
#define pb push_back
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<ii> vii;
typedef vector<iii> viii;

#ifndef DEBUG
#define cerr if (0) cerr
#endif

const int INF = 1000000005;
const ll LINF = 1000000000000000005ll;
const int MAXN = 200005;

int t;
int l, r;

int main() {
#ifndef DEBUG
    ios::sync_with_stdio(0), cin.tie(0);
#endif
    cin >> t;
    while (t--) {
        cin >> l >> r;
        if (l % 2 == 0 && (r - l) % 2 == 0) {
            cout << -1 << '\n';
            continue;
        }
        if ((r - l) % 2 == 0) {
            for (int i = l; i + 3 <= r; i += 2) {
                cout << i + 1 << ' ' << i << ' ';
            }
            cout << r << ' ' << r - 2 << ' ' << r - 1;
            cout << '\n';
        } else {
            for (int i = l; i <= r; i += 2) {
                cout << i + 1 << ' ' << i << ' ';
            }
            cout << '\n';
        }
    }
    return 0;
}