#include<bits/stdc++.h>
#define Gc() getchar()
#define Me(x,y) memset(x,y,sizeof(x))
#define Mc(x,y) memcpy(x,y,sizeof(x))
#define d(x,y) ((m)*(x-1)+(y))
#define R(n) (rnd()%(n)+1)
#define Pc(x) putchar(x)
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
#define eb emplace_back
#define all(x) x.begin(),x.end()
using namespace std;using ll=long long;using db=double;using lb=long db;using ui=unsigned;using ull=unsigned long long;using pii=pair<int,int>;
const int N=1e6+5,M=N*8+5,K=1000+5,mod=1e9+9,Mod=mod-1;const db eps=1e-8;const int INF=1e9+7;mt19937 rnd(263082);
#define Tp template<typename T>
#define Ts template<typename T,typename... Ar>
namespace Debug{
	Tp void _debug(char* f,T t){cerr<<f<<'='<<t<<endl;}
	Ts void _debug(char* f,T x,Ar... y){while(*f!=',') cerr<<*f++;cerr<<'='<<x<<",";_debug(f+1,y...);}
	#ifdef LOCAL
	#define gdb(...) _debug((char*)#__VA_ARGS__,__VA_ARGS__)
	#else 
	#define gdb(...) void()
	#endif
}using namespace Debug;
int n,m,vis[N],Ch;ll C[N],A[N],B[N];
vector<pair<ll,ll>> ans;
int dfs(int x){
	if(x==n) return 1;
	for(int i=1;i<=n;i++) if(!vis[i]) for(int j=i+1;j<=n;j++)if(!vis[j]&&(A[i]+A[j])%2==0){
		A[i]=(A[i]+A[j])/2;vis[j]=1;
		int op=dfs(x+1);
		A[i]=A[i]*2-A[j];vis[j]=0;
		if(op){
			ans.emplace_back(A[i],A[j]);
			return 1;
		}
	}
	return 0;
}
void Solve(){
	int i,j;scanf("%d",&n);m=n;Ch=0;
	for(i=1;i<=n;i++) scanf("%lld",&B[i]);
	sort(B+1,B+n+1);
	n=0;
	for(i=1;i<=m;i++){
		if(n<=2||B[i]^A[n-2]) A[++n]=B[i];
		else C[++Ch]=B[i];
	}
	ans.clear();
	if(!dfs(1)) puts("-1");
	else{
		reverse(ans.begin(),ans.end());
		for(i=1;i<=Ch;i++) printf("%lld %lld\n",C[i],C[i]);
		for(auto i:ans) printf("%lld %lld\n",i.fi,i.se);
	}
}
int main(){
    int t=1;
    scanf("%d",&t);
    while(t--) Solve();
    cerr<<clock()*1.0/CLOCKS_PER_SEC<<'\n';
}