#include<bits/stdc++.h>
using namespace std;
#define INF 0x3f3f3f3f
#define PI acos(-1)
#define io ios::sync_with_stdio(false); cin.tie(0); cout.tie(0)
#define mem(a,b) memset((a),(b),sizeof(a))
typedef long long ll;
typedef unsigned long long ull;
#define int long long
#define db long double

const double eps = 1e-6;
const int mod = 1e9 + 7;
const int maxn = 1e5 + 10;

int n;
struct node{
    int x, y, id;
    bool operator < (const node&A) const{
        if(x == A.x) return y < A.y;
        else return x < A.x;
    }
};

void solve() {
    cin >> n;
    vector<node> vec;
    for(int i = 1, u, v; i <= 3 * n; i++) {
        cin >> u >> v;
        vec.push_back({u, v, i});
    }
    sort(vec.begin(), vec.end());
    for(int i = 0; i < 3 * n; i += 3) {
        cout << vec[i].id << ' ' << vec[i + 1].id << ' ' << vec[i + 2].id << '\n';
    }
}

signed main(){
    io;
    int T = 1;
    cin >> T;
    while(T--) {
        solve();
    }
    return 0;
}