/*
    https://t.me/unstoppabIesoIvemachinechannel
    */
    #pragma ARCENIY_KIRILLOV_POVELITEL_KROKODILOV
    //#pragma comment(linker, "/stack:200000000")
    //#pragma GCC optimize("Ofast")
    //#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
    //#pragma GCC optimize("no-stack-protector")
    //#pragma GCC push_options
    //#pragma GCC optimize ("unroll-loops")
    //#pragma GCC pop_options
    //#pragma GCC target("popcnt")
    //#pragma GCC target("sse4")
    #include<bits/stdc++.h>
    #define fi first
    #define se second
    #define pb push_back
    #define eb emplace_back
    #define rng(a) a.begin(),a.end()
    #define fast ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
    #define rep(i, n) for (int i = 0; i < n; i++)
    #define per(i, n) for (int i = n - 1; i > -1; i--)
    #define rer(i, x, n) for (int i = x; i < n; i++)
    using namespace std;
    typedef long long ll;
    typedef pair<int, int> pii;
    typedef vector<int> vi;
    typedef vector<vi> vvi;
    typedef vector<pii> vp;
    typedef long double ld;















    signed main(){
        int n;
        cin >> n;
        vector<pair<pair<int,int>,pair<int,int> > > x(n);
        for (int i = 0; i < n; i++){
                cin >> x[i].fi.fi >> x[i].fi.se >> x[i].se.fi;
                x[i].se.se = i + 1;
        }
        sort(rng(x));
        vector<bool> used(n);
        for (int i = 0; i < n; i++){
                if (used[i]) continue;
            int minx, miny, minz, id;
            int maxx = minx = x[i].fi.fi;
            int maxy = miny = x[i].fi.se;
            int maxz = minz = x[i].se.fi;
            for (int j = i + 1; j < n; j++){
                if (used[j]) continue;
                    if ( ((minx <= x[j].fi.fi && x[j].fi.fi <= maxx) &&
                        (miny <= x[j].fi.se && x[j].fi.se <= maxy) &&
                        (minz <= x[j].se.fi && x[j].se.fi <= maxz)) || (maxx == minx && maxy == miny && maxz == minz) ){
                            id = j;
                            minx = min(minx, x[j].fi.fi);
                            maxx = max(maxx, x[j].fi.fi);
                            miny = min(miny, x[j].fi.se);
                            maxy = max(maxy, x[j].fi.se);
                            minz = min(minz, x[j].se.fi);
                            maxz = max(maxz, x[j].se.fi);
                        }
            }
            used[i] = 1;
            used[id] = 1;
            cout << x[i].se.se << ' ' << x[id].se.se << endl;
        }

    }