#include <bits/stdc++.h>
// clang-format off
using namespace std; using ll=long long; using ull=unsigned long long; using pll=pair<ll,ll>; const ll INF=4e18;
#define debug1(a) { cerr<<#a<<":"<<a<<endl; }
#define debug2(a,b) { cerr<<#a<<":"<<a<<" "<<#b<<":"<<b<<endl; }
#define debug3(a,b,c) { cerr<<#a<<":"<<a<<" "<<#b<<":"<<b<<" "<<#c<<":"<<c<<endl; }
#define debug4(a,b,c,d) { cerr<<#a<<":"<<a<<" "<<#b<<":"<<b<<" "<<#c<<":"<<c<<" "<<#d<<":"<<d<<endl; }

struct card_t { ll a; ll b; };
bool operator==(const card_t &lhs, const card_t &rhs) { return (lhs.a == rhs.a && lhs.b == rhs.b); }
bool operator!=(const card_t &lhs, const card_t &rhs) { return !(lhs == rhs); }
bool operator<(const card_t &lhs, const card_t &rhs) {
    if (lhs.a != rhs.a){return lhs.a<rhs.a;}
    return lhs.b<rhs.b;
}
card_t avg(card_t x, card_t y){
    return card_t{(x.a+y.a)/2,(x.b+y.b)/2};
}
std::ostream &operator<<(std::ostream &os, card_t &pt) {
    string s;
    s = "(" + to_string(ll(pt.a)) + ", " + to_string(ll(pt.b)) + ")";
    return os << s;
};
// clang-format on
namespace marathon {
mt19937 engine(0);
clock_t start_time;
double now() {
    return 1000.0 * (clock() - start_time) / CLOCKS_PER_SEC;
}
void marathon_init() {
    start_time = clock();
    random_device seed_gen;
    engine.seed(seed_gen());
}
int randint(int mn, int mx) {
    int rng = mx - mn + 1;
    return mn + (engine() % rng);
}
double uniform(double x, double y) {
    const int RND = 1e8;
    double mean = (x + y) / 2.0;
    double dif = y - mean;
    double p = double(engine() % RND) / RND;
    return mean + dif * (1.0 - 2.0 * p);
}
template <typename T>
T random_choice(vector<T> &vec) {
    return vec[engine() % vec.size()];
}
bool anneal_accept(double new_score, double old_score, double cur_time, double begin_time, double end_time, double begin_temp, double end_temp) {
    const int ANNEAL_RND = 1e8;
    const double ANNEAL_EPS = 1e-6;
    double temp = (begin_temp * (end_time - cur_time) + end_temp * (cur_time - begin_time)) / (end_time - begin_time);
    return (exp((new_score - old_score) / temp) > double(engine() % ANNEAL_RND) / ANNEAL_RND + ANNEAL_EPS);
}

}  // namespace marathon
const int OPLIMIT = 50;
const int N = 45;
const ll F17 = 500000000000000000;
card_t INIT_AB[N];
double evaluate(card_t x) {
    double da = abs(x.a - F17);
    double db = abs(x.b - F17);
    return max(da, db) * 100 + min(da, db);
}
double evaluate2(card_t x, card_t dest) {
    double da = abs(x.a - dest.a);
    double db = abs(x.b - dest.b);
    return max(da, db) * 100 + min(da, db);
}
void rec(vector<int> &ops, vector<bool> &used, pair<double, vector<int>> &best_result, card_t used_total, card_t target, int lastind, int maxops, vector<card_t> &now_cards) {
    if (ops.size() >= 1) {
        auto new_zero = avg(used_total, now_cards[lastind]);
        double e = evaluate(new_zero);
        if (e < best_result.first) {
            best_result = {e, ops};
        }
    }
    if (ops.size() >= maxops) {
        return;
    }
    for (int j = 0; j < N; j++) {
        if (used[j]) continue;
        used[j] = true;
        ops.push_back(j);
        card_t nxt_used_total = (used_total.a <= 0) ? now_cards[j] : avg(now_cards[j], used_total);
        rec(ops, used, best_result, nxt_used_total, target, lastind, maxops, now_cards);
        ops.pop_back();
        used[j] = false;
    }
}
void do_op(int i, int j, vector<card_t> &now_cards, vector<pair<int, int>> &result) {
    card_t avg_ = avg(now_cards[i], now_cards[j]);
    now_cards[i] = avg_;
    now_cards[j] = avg_;
    result.push_back({i, j});
}
void output(vector<pair<int, int>> &result) {
    cout << result.size() << endl;
    for (auto p : result) {
        cout << p.first + 1 << " " << p.second + 1 << endl;
    }
}
vector<int> anneal(vector<card_t> &now_cards) {
    vector<int> ops;
    auto avgscore = [&]() {
        int m = ops.size();
        ll a = 0;
        ll b = 0;
        if (ops.size() == 1) {
            return -evaluate(avg(now_cards[ops.back()], now_cards[0]));
        } else {
            for (int i = 0; i < m; i++) {
                if (i == m - 1) {
                    a += now_cards[ops[i]].a / (2 << (m - 2));
                    b += now_cards[ops[i]].b / (2 << (m - 2));
                } else {
                    a += now_cards[ops[i]].a / (2 << i);
                    b += now_cards[ops[i]].b / (2 << i);
                }
            }
            return -evaluate({(a + now_cards[0].a) / 2, (b + now_cards[0].b) / 2});
        }
    };
    {
        vector<bool> used(N);
        for (int it = 0; it < 25; it++) {
            pair<double, int> best = {-1e50, -1};
            for (int u = 1; u < N; u++) {
                if (used[u]) continue;
                ops.push_back(u);
                pair<double, int> now = {avgscore(), u};
                best = max(now, best);
                ops.pop_back();
            }
            if (it < 10 || best.second >= 0) {
                used[best.second] = true;
                ops.push_back(best.second);
            }
        }
    }
    double ini_score = avgscore();
    double old_score = ini_score;
    double begin_time = marathon::now();
    double end_time = begin_time + 300;
    int anneal_iter = 0;
    int anneal_accepted = 0;
    pair<double, vector<int>> best = {ini_score, ops};
    vector<double> temps;
    double begin_temp = 1;
    double end_temp = 1;
    auto update_temps = [&](double _new_score) {
    };
    //     temps.push_back(abs(_new_score - old_score));
    //     int cnt = 0;
    //     double sum = 0;
    //     for (int it = max(0, int(temps.size()) - 10); it < temps.size(); it++) {
    //         cnt++;
    //         sum += temps[it];
    //     }
    //     begin_temp = 0.0001 * sum / cnt;
    //     end_temp = 0.1 * begin_temp;
    // };
    while (marathon::now() < end_time) {
        anneal_iter++;
        int x = 1 + marathon::engine() % (N - 1);
        int y = 1 + marathon::engine() % (N - 1);
        if (x == y) continue;
        int xi = -1;
        int yi = -1;
        for (int i = 0; i < int(ops.size()); i++) {
            if (ops[i] == x) xi = i;
            if (ops[i] == y) yi = i;
        }
        if (xi < 0 && yi < 0) continue;
        if (xi < 0 && yi >= 0) {
            swap(x, y);
            swap(xi, yi);
        }
        if (xi >= 0 && yi < 0) {
            ops[xi] = y;
            double new_score = avgscore();
            update_temps(new_score);
            // if (marathon::anneal_accept(new_score, old_score, marathon::now(), begin_time, end_time, begin_temp, end_temp)) {
            if (new_score >= old_score) {
                anneal_accepted++;
                old_score = new_score;
            } else {
                ops[xi] = x;
            }
            if (new_score > best.first) {
                best = {new_score, ops};
            }
        } else {
            swap(ops[xi], ops[yi]);
            double new_score = avgscore();
            update_temps(new_score);
            if (new_score >= old_score) {  // if (marathon::anneal_accept(new_score, old_score, marathon::now(), begin_time, end_time, begin_temp, end_temp)) {
                anneal_accepted++;
                old_score = new_score;
            } else {
                swap(ops[xi], ops[yi]);
            }
            if (new_score > best.first) {
                best = {new_score, ops};
            }
        }
    }
    debug4(ini_score, best.first, anneal_iter, anneal_accepted);
    return best.second;
}
void solve() {
    vector<card_t> now_cards(N);
    for (int i = 0; i < N; i++) {
        now_cards[i] = INIT_AB[i];
    }
    vector<pair<int, int>> result;
    while (result.size() + 25 <= OPLIMIT) {
        auto ops = anneal(now_cards);

        auto work_cards = now_cards;
        auto work_result = result;
        int m = ops.size();
        for (int i = m - 1; i >= 1; i--) {
            do_op(ops[i], ops[i - 1], work_cards, work_result);
        }
        do_op(0, ops[0], work_cards, work_result);
        if (evaluate(work_cards[0]) < evaluate(now_cards[0])) {
            now_cards = work_cards;
            result = work_result;
        } else {
            break;
        }
        debug2(result.size(), now_cards[0]);
    }
    output(result);
}
int main() {
    marathon::marathon_init();
    int n;
    cin >> n;
    for (int i = 0; i < n; i++) {
        ll a, b;
        cin >> a >> b;
        INIT_AB[i] = card_t{a, b};
    }
    solve();
    return 0;
}