#include<bits/stdc++.h>
#define ll long long
using namespace std;
mt19937 rnd(2);
int n;
ll b[1000005];
vector<ll> a[2];
vector<pair<ll,ll> > res;
void work(vector<ll>&v){
    ll x=v.back();v.pop_back();
    ll y=v.back();v.pop_back();
    res.emplace_back(x,y);
    a[x+y>>1&1].push_back(x+y>>1);
}
bool work(){
    shuffle(b+1,b+n+1,rnd);
    a[0].clear(),a[1].clear(),res.clear();
    for(int i=1;i<=n;++i)a[b[i]&1].push_back(b[i]);
    while(a[0].size()>1||a[1].size()>1){
        int p=rnd()&1;
        if(a[p].size()>1) work(a[p]);
        else work(a[p^1]);
    }
    if(!a[0].size()||!a[1].size()){
        for(auto i:res)
			printf("%lld %lld\n",i.first,i.second);
        return true;
    }
    return false;
}
int main(){
//	freopen("meow.in","r",stdin);
//	freopen("meow.out","w",stdout);
    int T;scanf("%d",&T);
    while(T--){
	    scanf("%d",&n);
	//    bool even=true;
	    for(int i=1;i<=n;i++){
			scanf("%lld",b[i]);
	//		if(b[i]%2) even=false;
		}
	//	if(T>100 || !even) continue;
	    bool flag=false;
	    for(int i=1;i<=300;i++)
	        if(work()){
				flag=true;
				break;
			}
	    if(!flag)
			puts("-1");
	}
	return 0;
}