#include <iostream>
#include <vector>
#include <random>

static std::mt19937 mt(0);
static std::vector<long> a, b;

using Entry = std::pair<int, int>;
using Solution = std::vector<Entry>;

long calc_score(const Solution& ans, const std::vector<long>& a, const std::vector<long>& b) {
    std::vector<long> aa = a;
    std::vector<long> bb = b;
    for (auto [u,v] : ans) {
        long v1 = (aa[u] + aa[v])/2;
        long v2 = (bb[u] + bb[v])/2;
        aa[u] = v1;
        aa[v] = v1;
        bb[u] = v2;
        bb[v] = v2;
    }
    double v1 = std::abs(aa[0] - 5*1e17);
    double v2 = std::abs(bb[0] - 5*1e17);
    long score = 2000000L - 100000L * std::log10(std::max(v1, v2) + 1);
    return score;
}

void print_ans(const Solution& ans) {
    std::cout << ans.size() << std::endl;
    for (auto [u,v] : ans) {
        std::cout << u+1 << " " << v+1 << std::endl;
    }
}

auto gen_random_ans(int n) {
    constexpr int m = 50;
    std::vector<Entry> ans;
    for (int i = 0; i < m; i++) {
        int u, v;
        while (true) {
            u = mt() % n;
            v = mt() % n;
            if (u != v) {
                break;
            }
        }
        ans.emplace_back(u,v);
    }
    return ans;
}

auto greedy_ans(int n) {
    constexpr int m = 50;
    std::vector<Entry> ans;
    long best_score = calc_score(ans, a, b);
    std::cerr << "initial score: " << best_score << std::endl;
    for (int i = 0; i < m; i++) {
        std::cerr << i << " th iter" << std::endl;
        int u = 0;
        int best_v = -1;
        for (int v = 1; v < n; v++) {
            ans.emplace_back(u,v);
            long score = calc_score(ans, a, b);
            std::cerr << "v, score: " << v << ", " << score << std::endl;
            if (score > best_score) {
                best_score = score;
                best_v = v;
            }
            ans.pop_back();
        }
        std::cerr << "best v, score: " << best_v << ", " << best_score << std::endl;
        if (best_v == -1) {
            break;
        }
        else {
            ans.emplace_back(u,best_v);
        }
    }
    return ans;
}

int main() {
    int n;
    std::cin >> n;

    a.resize(n);
    b.resize(n);
    for (int i = 0; i < n; i++) {
        std::cin >> a[i] >> b[i];
    }

    auto ans = greedy_ans(n);
    std::cerr << "Final score: " << calc_score(ans, a, b) << std::endl;
    print_ans(ans);
}