#include<bits/stdc++.h>
using namespace std;
int n,m;
struct nod{int x,y,i;}s[300001];
bool cmp1(nod a,nod b){return a.x<b.x;}
bool cmp2(nod a,nod b){return a.y<b.y;}
int main(){
	int T;cin>>T;
	while(T--){
		cin>>n;
		for(int i=1;i<=n;i++)cin>>s[i].x>>s[i].y,s[i].i=i;
		sort(s+1,s+1+n,cmp1);
		sort(s+1,s+1+n/2,cmp2);sort(s+n/2+1,s+n+1,cmp2);
		for(int i=1;i<=n/2;i++){
			cout<<s[i].i<<" "<<s[n-i+1].i<<"\n";
		}
	}
	return 0;
}