#include <iostream>
#include <algorithm>
#include<cmath>
#include<cstring>
#include<cstdio>
#include<cstdlib>
#include<vector>
#include<iomanip>
#include<ctime>
#include<set>
#include<map>
#include<queue>
#include<stack>
#include<bitset>
#include<cassert>
#define sqr(x) ((x)*(x))
#define fz1(i,n) for ((i)=1;(i)<=(n);(i)++)
#define fd1(i,n) for ((i)=(n);(i)>=1;(i)--)
#define fz0g(i,n) for ((i)=0;(i)<=(n);(i)++)
#define fd0g(i,n) for ((i)=(n);(i)>=0;(i)--)
#define fz0k(i,n) for ((i)=0;(i)<(n);(i)++)
#define fd0k(i,n) for ((i)=(((long long)(n))-1);(i)>=0;(i)--)
#define fz(i,x,y) for ((i)=(x);(i)<=(y);(i)++)
#define fd(i,y,x) for ((i)=(y);(i)>=(x);(i)--)
#define fzin fz1(i,n)
#define fzim fz1(i,m)
#define fzjn fz1(j,n)
#define fzjm fz1(j,m)
#define ff(c,itr) for (__typeof((c).begin()) itr=(c).begin();itr!=(c).end();++itr)
#define pb push_back
#define mk make_pair
#define rdst(st,len){static char ss[len];scanf(" %s",ss);(st)=ss;}
#define spln(i,n) (i==n?'\n':' ')
#define fac_init(n){fac[0]=fac[1]=inv[1]=fi[0]=fi[1]=1;fz(i,2,n){fac[i]=1ll*fac[i-1]*i%mod;inv[i]=1ll*(mod-mod/i)*inv[mod%i]%mod;fi[i]=1ll*fi[i-1]*inv[i]%mod;}}
using namespace std;
typedef long long i64;
typedef long double f80;
typedef unsigned int u32;
typedef unsigned long long u64;
//typedef __int128 i128;
//typedef unsigned __int128 u128;
#ifndef ONLINE_JUDGE
	FILE *___=freopen("1.in","r",stdin);
#endif
inline void read(int &x)
{
	char c;int f=1;
	while(!isdigit(c=getchar()))if(c=='-')f=-1;
	x=(c&15);while(isdigit(c=getchar()))x=(x<<1)+(x<<3)+(c&15);
	x*=f;
}
inline void read(i64 &x)
{
	char c;int f=1;
	while(!isdigit(c=getchar()))if(c=='-')f=-1;
	x=(c&15);while(isdigit(c=getchar()))x=(x<<1)+(x<<3)+(c&15);
	x*=f;
}
int t,n,m,i,j;
vector<i64> a;
vector<i64> v0,v1;
vector<pair<i64,i64> > cur;
bool hv;
void dfs()
{
	if(a.size()==1){
		hv=1;return;
	}
	int i,j;
	fz0k(i,a.size())fz(j,i+1,a.size()-1)if((a[i]+a[j])%2==0){
		i64 ti=a[i],tj=a[j],tk=a.back();
		cur.push_back(make_pair(a[i],a[j]));
		a[i]=(a[i]+a[j])/2;
		swap(a[j],a.back());a.pop_back();
		dfs();if(hv)return;
		a.push_back(tk);a[i]=ti;a[j]=tj;
		cur.pop_back();
	}
}
int main()
{
	read(t);
	while(t--){
		a.clear();v0.clear();v1.clear();
		read(n);fz1(i,n){i64 x;read(x);a.push_back(x);}
		bool flg0=1,flg1=1;ff(a,it)if((*it)&1)flg0=0;else flg1=0;
		if(flg0||flg1){
			ff(a,it) if((*it)%4<2)v0.push_back(*it);else v1.push_back(*it);
			while(v0.size()>=2||v1.size()>=2){
				if(v0.size()>=2){
					i64 x=v0.back();v0.pop_back();
					i64 y=v0.back();v0.pop_back();
					printf("%lld %lld\n",x,y);
					i64 t=(x+y)/2;if(t%4<2)v0.push_back(t);else v1.push_back(t);
				}
				else{
					i64 x=v1.back();v1.pop_back();
					i64 y=v1.back();v1.pop_back();
					printf("%lld %lld\n",x,y);
					i64 t=(x+y)/2;if(t%4<2)v0.push_back(t);else v1.push_back(t);
				}
			}
			if(v0.size()&&v1.size()) printf("%lld %lld\n",v0.back(),v1.back());
			continue;
		}
		hv=0;cur.clear();dfs();
		if(hv){
			ff(cur,it) printf("%lld %lld\n",it->first,it->second);
		}
		else{
			puts("-1");
		}
	}
	return 0;
}