#include<bits/stdc++.h>
using namespace std;
mt19937 rnd(time(0));
typedef long long ll;
const int N=1e6+5;
int T,n;ll a[N];vector<ll> t[2];
vector<pair<ll,ll> > opt;
bool solve(){
    opt.clear();t[0].clear();t[1].clear();
    shuffle(a+1,a+n+1,rnd);
    for(int i=1;i<=n;i++)
        t[a[i]&1].push_back(a[i]);
    for(int i=1;i<n;i++){
        if(t[0].size()==1&&t[1].size()==1)return false;
        vector<int> s{0,1};if(rnd()&1)swap(s[0],s[1]);
        for(int j:s)if(t[j].size()>=2){
            ll x=t[j].back(),y;t[j].pop_back();
            y=t[j].back();t[j].pop_back();
            opt.push_back({x,y});
            (x+=y)>>=1;t[x&1].push_back(x);
            break;
        }
    }
    for(auto x:opt)printf("%lld %lld\n",x.first,x.second);
    return true;
}
int main(){
    // freopen("cow.in","r",stdin);
    // freopen("cow.out","w",stdout);
    scanf("%d",&T);
    while(T--){
        scanf("%d",&n);
        for(int i=1;i<=n;i++)scanf("%lld",a+i);
        int test=400,flag=0;
        while(test--)if(solve()){flag=1;break;}
        if(!flag)printf("-1\n");
    }
    return 0;
}