#include<cstdio>
#include<vector>
#include<queue>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<ctime>
#include<random>
#include<array>
#include<set>
#include<assert.h>
#define pb emplace_back
#define mp make_pair
#define fi first
#define se second
#define dbg(x) cerr<<"In Line "<< __LINE__<<" the "<<#x<<" = "<<x<<'\n'
#define dpi(x,y) cerr<<"In Line "<<__LINE__<<" the "<<#x<<" = "<<x<<" ; "<<"the "<<#y<<" = "<<y<<'\n'
#define DE(fmt,...) fprintf(stderr, "Line %d : " fmt "\n",__LINE__,##__VA_ARGS__)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int>pii;
typedef pair<ll,int>pli;
typedef pair<ll,ll>pll;
typedef pair<int,ll>pil;
typedef vector<int>vi;
typedef vector<ll>vll;
typedef vector<pii>vpii;
typedef vector<pll>vpll;
template<typename T>T cmax(T &x, T y){return x=x>y?x:y;}
template<typename T>T cmin(T &x, T y){return x=x<y?x:y;}
template<typename T>
T &read(T &r){
	r=0;bool w=0;char ch=getchar();
	while(ch<'0'||ch>'9')w=ch=='-'?1:0,ch=getchar();
	while(ch>='0'&&ch<='9')r=r*10+(ch^48),ch=getchar();
	return r=w?-r:r;
}
template<typename T1,typename... T2>
void read(T1 &x,T2& ...y){read(x);read(y...);}
mt19937 rnd(0);
const int N=1000010;
int n;
ll a[N];
void solve(){
	read(n);
	for(int i=1;i<=n;i++)read(a[i]);
	vpll ans;
	for(int w=1;w<=700;w++){
		vpll().swap(ans);
		shuffle(a+1,a+n+1,rnd);
		vll vec[2];
		for(int i=1;i<=n;i++)vec[a[i]&1].pb(a[i]);
		int fl=1;
		for(int i=1;i<n;i++){
			int o=rnd()%2;
			if((int)vec[o].size()<=1)o^=1;
			if(vec[o].size()==1){
				fl=0;
				break;
			}
			ll x=vec[o].back();vec[o].pop_back();
			ll y=vec[o].back();vec[o].pop_back();
			ans.pb(x,y);
			x=(x+y)/2;
			vec[x&1].pb(x);
		}
		if(fl){
			for(auto i:ans)cout<<i.fi<<' '<<i.se<<'\n';
			return ;
		}
	}
	puts("-1");
}
signed main(){
	int T;read(T);
	while(T--)solve();	
    #ifdef do_while_true
//		cerr<<'\n'<<"Time:"<<1.0*clock()/CLOCKS_PER_SEC*1000<<" ms"<<'\n';
	#endif
	return 0;
}