#include<iostream>
#include<cstdio>
#include<vector>
#include<queue>
#define N 1000000
using namespace std;
long long read()
{
    char c=0;
    long long sum=0;
    while (c<'0'||c>'9') c=getchar();
    while ('0'<=c&&c<='9') sum=sum*10+c-'0',c=getchar();
    return sum;
}
struct reads
{
    long long x,y;
};
reads dque[N+1];
int T,n,top,cnt[N+1];
long long a[N+1];
bool op;
void solve(vector<long long>p)
{
    if (p.size()==1)
    {
	op=1;
	for (int i=1;i<=top;++i) printf("%lld %lld\n",dque[i].x,dque[i].y);
	return;
    }
    vector<long long>q;
    for (int i=0;i<p.size();++i)
	for (int j=i+1;j<p.size();++j)
	    if (!((p[i]+p[j])&1))
	    {
		q.clear(),dque[++top]=(reads){p[i],p[j]},q.push_back((p[i]+p[j])>>1);
		for (int k=0;k<p.size();++k)
		    if (k!=i&&k!=j)
			q.push_back(p[k]);
		solve(q),top--;
		if (op) return;
	    }
    return;
}
int main()
{
    long long tops,tops2,maxn;
    vector<long long>p;
    queue<long long>A;
    queue<long long>B;
    T=read();
    while (T--)
    {
	n=read(),maxn=0;
	for (int i=1;i<=n;++i) a[i]=read(),maxn=max(maxn,a[i]);
	if (n<=7)
	{
	    op=top=0,p.clear();
	    for (int i=1;i<=n;++i) p.push_back(a[i]);
	    solve(p);
	    if (!op) puts("-1");
	}
	else if (maxn<=10)
	{
	    op=top=0,p.clear();
	    for (int i=0;i<=10;++i) cnt[i]=0;
	    for (int i=1;i<=n;++i) cnt[a[i]]++;
	    for (int i=0;i<=10;++i)
	    {
		for (int j=1;j<=cnt[i]-3;++j) dque[++top]=(reads){i,i};
		for (int j=1;j<=min(cnt[i],3);++j) p.push_back(i);
	    }
	    solve(p);
	    if (!op) puts("-1");
	}
	else
	{
	    while (!A.empty()) A.pop();
	    while (!B.empty()) B.pop();
	    for (int i=1;i<=n;++i)
	    {
		if (a[i]%4==0) A.push(a[i]);
		else B.push(a[i]);
	    }
	    while (A.size()+B.size()>=2)
	    {
		if (A.size()>=2)
		{
		    tops=A.front(),A.pop(),tops2=A.front(),A.pop(),printf("%lld %lld\n",tops,tops2);
		    if (((tops+tops2)>>1)%4==0) A.push((tops+tops2)>>1);
		    else B.push((tops+tops2)>>1);
		}
		else if (B.size()>=2)
		{
		    tops=B.front(),B.pop(),tops2=B.front(),B.pop(),printf("%lld %lld\n",tops,tops2);
		    if (((tops+tops2)>>1)%4==0) A.push((tops+tops2)>>1);
		    else B.push((tops+tops2)>>1);
		}
		else tops=A.front(),A.pop(),tops2=B.front(),B.pop(),printf("%lld %lld\n",tops,tops2);
	    }
	}
    }
    return 0;
}