#include <bits/stdc++.h>
using namespace std;
int read(){
	char c=getchar();int x=0;
	while(c<48||c>57) c=getchar();
	do x=(x<<1)+(x<<3)+(c^48),c=getchar();
	while(c>=48&&c<=57);
	return x;
}
typedef vector<int> vi;
set<vi> vis;
map<vi,pair<vi,pair<int,int> > > mp;
void dfs(vi cur){
	if(vis.find(cur)!=vis.end()) return;
	vis.emplace(cur);
	if(cur.size()==1u){mp[cur]=make_pair(vi(),make_pair(0,0));return;}
	int len(cur.size());
	for(int i=0;i<len;++i)
		for(int j=i+1;j<len;++j){
			if((cur[i]^cur[j])&1) continue;
			vector<int> tmp;
			for(int k=0;k<len;++k)
				if(k!=i&&k!=j) tmp.emplace_back(cur[k]);
			tmp.emplace_back((cur[i]+cur[j])>>1);
			sort(tmp.begin(),tmp.end());
			dfs(tmp);
			if(mp.find(tmp)!=mp.end()){
				mp[cur]=make_pair(tmp,make_pair(cur[i],cur[j]));
				return;
			}
		}
	return;
}
int main(){
	int tc=read();
	while(tc--){
		int n=read();
		vi cur(n);
		for(int i=0;i<n;++i) cur[i]=read();
		sort(cur.begin(),cur.end());
		dfs(cur);
		if(mp.find(cur)==mp.end()){puts("-1");continue;}
		for(int i=1;i<n;++i){
			printf("%d %d\n",mp[cur].second.first,mp[cur].second.second);
			cur=mp[cur].first;
		}
	}
	return 0;
}