#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,length,length2,leng;
long long a[N+1],tong[N+1],tong2[N+1],tmp[N+1];
bool opt;
void solve(vector<long long>p)
{
    if (p.size()==1)
    {
	opt=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 (opt) return;
	    }
    return;
}
int main()
{
    int rt,rt2,x,y;
    long long tops,tops2;
    bool op,op2;
    queue<long long>A;
    queue<long long>B;
    vector<long long>p;
    T=read();
    while (T--)
    {
	n=read(),length=length2=opt=top=0;
	for (int i=1;i<=n;++i)
	{
	    a[i]=read();
	    if (!(a[i]&1)) tong[++length]=a[i];
	    else tong2[++length2]=a[i];
	}
	rt=0;
	for (int i=1;i<=min(59,length-1);++i)
	{
	    op=op2=0;
	    for (int j=1;j<=length;++j)
	    {
		if (!(tong[j]&(1ll<<i))) op=1;
		else op2=1;
	    }
	    if (op&&op2)
	    {
		rt=i;
		break;
	    }
	}
	rt2=0;
	for (int i=1;i<=min(59,length2-1);++i)
	{
	    op=op2=0;
	    for (int j=1;j<=length2;++j)
	    {
		if (!(tong2[j]&(1ll<<i))) op=1;
		else op2=1;
	    }
	    if (op&&op2)
	    {
		rt2=i;
		break;
	    }
	}
	for (int i=rt;i>=1;--i)
	{
	    leng=x=y=0;
	    for (int j=1;j<=length;++j)
	    {
		if (!(tong[j]&(1ll<<i))) x=j;
		else y=j;
	    }
	    dque[++top]=(reads){tong[x],tong[y]};
	    for (int j=1;j<=length;++j)
		if (j!=x&&j!=y)
		    tmp[++leng]=tong[j];
	    tmp[++leng]=(tong[x]+tong[y])>>1,length=leng;
	    for (int j=1;j<=length;++j) tong[j]=tmp[j];
	}
	for (int i=rt2;i>=1;--i)
	{
	    leng=x=y=0;
	    for (int j=1;j<=length2;++j)
	    {
		if (!(tong2[j]&(1ll<<i))) x=j;
		else y=j;
	    }
	    dque[++top]=(reads){tong2[x],tong2[y]};
	    for (int j=1;j<=length2;++j)
		if (j!=x&&j!=y)
		    tmp[++leng]=tong2[j];
	    tmp[++leng]=(tong2[x]+tong2[y])>>1,length2=leng;
	    for (int j=1;j<=length2;++j) tong2[j]=tmp[j];
	}
	for (int i=1;i<=length;++i)
	{
	    if (tong[i]%4==0) A.push(tong[i]);
	    else B.push(tong[i]);
	}
	while (A.size()>=3||B.size()>=3)
	{
	    if (A.size()>=3) tops=A.front(),A.pop(),tops2=A.front(),A.pop();
	    else tops=B.front(),B.pop(),tops2=B.front(),B.pop();
	    dque[++top]=(reads){tops,tops2};
	    if (((tops+tops2)>>1)%4==0) A.push((tops+tops2)>>1);
	    else B.push((tops+tops2)>>1);
	}
	length=0;
	while (!A.empty()) tong[++length]=A.front(),A.pop();
	while (!B.empty()) tong[++length]=B.front(),B.pop();
	for (int i=1;i<=length2;++i)
	{
	    if (tong2[i]%4==1) A.push(tong2[i]);
	    else B.push(tong2[i]);
	}
	while (A.size()>=3||B.size()>=3)
	{
	    if (A.size()>=3) tops=A.front(),A.pop(),tops2=A.front(),A.pop();
	    else tops=B.front(),B.pop(),tops2=B.front(),B.pop();
	    dque[++top]=(reads){tops,tops2};
	    if (((tops+tops2)>>1)%4==1) A.push((tops+tops2)>>1);
	    else B.push((tops+tops2)>>1);
	}
	while (!A.empty()) tong[++length]=A.front(),A.pop();
	while (!B.empty()) tong[++length]=B.front(),B.pop();
	p.clear();
	for (int i=1;i<=length;++i) p.push_back(tong[i]);
	solve(p);
	if (!opt) puts("-1");
    }
    return 0;
}