#include<bits/stdc++.h>
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
#define pii pair<ll,ll>
#define rep(i,a,b) for(ll i=(a);i<=(b);++i)
#define per(i,a,b) for(ll i=(a);i>=(b);--i)
using namespace std;
bool Mbe;
ll read(){
    ll x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}
void write(ll x){
    if(x<0)putchar('-'),x=-x;
    if(x>9)write(x/10);
    putchar(x%10+'0');
}
const ll N=1e6+9;
ll T,n,a[N];
mt19937_64 rnd(time(0));
void solve(){
    n=read();
    rep(i,1,n)a[i]=read();
    ll rd=500;
    while(rd--){
        shuffle(a+1,a+n+1,rnd);
        vector<ll>s[2];
        rep(i,1,n)s[a[i]&1].emplace_back(a[i]);
        vector<pii>res;
        ll fl=1;
        rep(i,1,n-1){
            ll o=rnd()&1;
            if((ll)s[o].size()<2)o^=1;
            if((ll)s[o].size()<2){
                fl=0;
                break;
            }
            ll p=s[o].back();
            s[o].pop_back();
            ll q=s[o].back();
            s[o].pop_back();
            ll nw=(p+q)/2;
            s[nw&1].push_back(nw);
            res.push_back(make_pair(p,q));
        }
        if(fl){
            for(pii p:res)write(p.first),putchar(' '),write(p.second),putchar('\n');
            return ;
        }
    }
    puts("-1");
}
bool Med;
int main(){
    cerr<<fabs(&Med-&Mbe)/1048576.0<<"MB\n";
    T=read();
    while(T--)solve();
    return 0;
}