#include <atcoder/all>
#include <bits/stdc++.h>
using ll = long long;
using ull = unsigned long long;
#define rep(i, n) for(int i = 0; i < (int)(n); i++)
#define REP(i, m, n) for(int i = (int)(m); i < (int)(n); i++)
using namespace std;
using namespace atcoder;
using mint = modint998244353;
const int inf = 1000000007;
const ll longinf = 1ll << 60;

struct Timer {
    chrono::system_clock::time_point start, last_updated;

    Timer() {
        start = chrono::system_clock::now();
        last_updated = chrono::system_clock::now();
    }

    void reset() {
        start = chrono::system_clock::now();
    }

    void update() {
        last_updated = chrono::system_clock::now();
    }

    double getTime() {
        auto now = chrono::system_clock::now();
        return chrono::duration<double>(now - start).count();
    }
    double should_finish_search1() {
        return getTime() > 5.8;
    }
    bool should_reset() {
        auto now = chrono::system_clock::now();
        return chrono::duration<double>(now - last_updated).count() > 1.0 ||
               chrono::duration<double>(now - start).count() > 5.8;
    }
};

Timer timer;
struct Xor128 {
    unsigned x, y, z, w;

    Xor128() : x(123456789), y(362436069), z(521288629), w(88675123){};

    inline unsigned xor128() {
        unsigned t;
        t = x ^ (x << 11);
        x = y;
        y = z;
        z = w;
        return w = (w ^ (w >> 19)) ^ (t ^ (t >> 8));
    }

    int nextInt(int x, int y) {
        return xor128() % (y - x) + x;
    }

    double nextDouble(double a, double b) {
        return (double)(xor128() & 0xffff) / 0xffff * (b - a) + a;
    }
};
auto rnd = Xor128();

double calculate_score(ll x) {
    return 2000000 - 100000 * log10(abs(x - (ll)5e17) + 1);
}

void output(vector<pair<int, int>> &query) {
    for(auto [l, r] : query) {
        cout << l + 1 << " " << r + 1 << endl;
    }
}

void do_query(vector<ll> &a, vector<ll> &b, int i, int j) {
    ll x = (a[i] + a[j]) / 2;
    ll y = (b[i] + b[j]) / 2;
    a[i] = a[j] = x;
    b[i] = b[j] = y;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int n;
    cin >> n;
    vector<ll> a(n), b(n);
    rep(i, n) cin >> a[i] >> b[i];
    vector<pair<int, int>> best_query;
    double best_score = 0;
    rep(__, 100000) {
        vector<ll> c = a, d = b;
        vector<pair<int, int>> query;
        rep(_, 50) {
            int x = rnd.nextInt(0, n), y = rnd.nextInt(0, n - 1);
            if(y >= x)
                ++y;
            if(rnd.nextInt(0, 2) == 0) {
                x = 0;
                y = rnd.nextInt(1, n);
            }
            do_query(c, d, x, y);
            query.push_back({x, y});
        }
        double ret = min(calculate_score(c[0]), calculate_score(d[0]));
        if(ret > best_score) {
            best_score = ret;
            best_query = query;
        }
    }
    output(best_query);
    for(auto [l, r] : best_query) {
        do_query(a, b, l, r);
    }
    cerr << 50 * min(calculate_score(a[0]), calculate_score(b[0])) << endl;
    return 0;
}