#include <bits/stdc++.h>
using namespace std;
#define ll long long

ll gcd(ll x, ll y) {
    if(y == 0) return x;
    return gcd(y, x % y);
}

int main() {
    ll T; cin >> T;
    for(ll t = 0; t < T; t++) {
        ll L, R; cin >> L >> R;

        if(L == R) {
            cout << "-1\n"; continue;
        }

        // if even: always possible.

        if((R - L + 1)%2  == 0) {
            goodcase:
            for(ll i = L; i <= R; i += 2) {
                cout << i+1 << " " << i << " ";
            }
            cout << "\n";
            continue;
        }
        // evens > odds: always impossible.
        // o.w. possible. (3-cycle involving odds, and then evens.)

        if(!(L%2)) {
            cout << -1 << "\n"; continue;
        }

        cout << L+2 << " " << L << " " << L+1 << " "; L += 3;
        goto goodcase;
    }


}