// #pragma GCC target("avx2")
#pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")
#include<bits/stdc++.h>
// #include<sys/time.h>
// #include<atcoder/segtree>


using namespace std;

// using mint = atcoder::modint998244353;

const int M = 998244353;
const long long LM = 1LL << 60;

using P = pair<int, int>;

pair<vector<P>, long long> solve(vector<long long> a, vector<long long> b, int L) {
    int n = a.size();
    long long T = 500000000000000000LL;
    auto calc = [&](int i, int j) {
        return max(abs(a[i] + a[j] - T * 2), abs(b[i] + b[j] - T * 2));
    };
    vector<P> ans;
    auto op = [&](int i, int j) {
        if (i == j) return;
        if (ans.size() >= 50) return;
        ans.emplace_back(i, j);
        auto av = (a[i] + a[j]) / 2;
        auto bv = (b[i] + b[j]) / 2;
        a[i] = av;
        a[j] = av;
        b[i] = bv;
        b[j] = bv;
    };
    // auto calc2 = [&](int i, int j) {
    //     return abs(a[i] + a[j] - T * 2) + abs(b[i] + b[j] - T * 2);
    // };
    while ((int)ans.size() < L) {
        int p = -1, q = -1;
        for (int i = 0; i < n; ++i) {
            for (int j = i + 1; j < n; ++j) {
                if (calc(i, j) < calc(i, i) && calc(i, j) < calc(j, j)) {
                    if (p == -1 || calc(i, j) < calc(p, q)) {
                        p = i;
                        q = j;
                    }
                }
            }
        }
        if (p == -1) break;
        op(p, q);
    }
    auto greedy = [&]() {
        while (ans.size() < 50) {
            int q = 0;
            for (int i = 1; i < n; ++i) {
                if (calc(0, q) > calc(0, i)) {
                    q = i;
                }
            }
            if (q == 0) break;
            op(0, q);
        }
    };
    auto orig_a = a;
    auto orig_b = b;
    auto orig_ans = ans;
    greedy();

    auto best_ans = ans;
    auto best_score = calc(0, 0);
    for (int i = 1; i < n; ++i) {
        a = orig_a;
        b = orig_b;
        ans = orig_ans;
        op(0, i);
        greedy();
        if (best_score > calc(0, 0)) {
            best_ans = ans;
            best_score = calc(0, 0);
        }
    }
    for (int i = 1; i < n; ++i) {
        for (int j = 1; j < n; ++j) {
            if (i == j) continue;
            a = orig_a;
            b = orig_b;
            ans = orig_ans;
            op(0, i);
            op(0, j);
            greedy();
            if (best_score > calc(0, 0)) {
                best_ans = ans;
                best_score = calc(0, 0);
            }
        }
    }
    for (int i = 1; i < n; ++i) {
        for (int j = 1; j < n; ++j) {
            if (i == j) continue;
            for (int k = 1; k < n; ++k) {
                if (j == k) continue;
                a = orig_a;
                b = orig_b;
                ans = orig_ans;
                op(0, i);
                op(0, j);
                op(0, k);
                greedy();
                if (best_score > calc(0, 0)) {
                    best_ans = ans;
                    best_score = calc(0, 0);
                }
            }
        }
    }
    ans = best_ans;
    return { ans, best_score };

}


int main() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    int n;
    cin >> n;
    vector<long long> a(n), b(n);
    for (int i = 0; i < n; ++i) {
        cin >> a[i] >> b[i];
    }
    vector<P> ans;
    long long score = LM;
    for (int i = 5; i <= 40; i += 5) {
        auto res = solve(a, b, i);
        if (score > res.second) {
            ans = res.first;
            score = res.second;
            cerr << i << '\n';
        }
    }


    if (ans.size() > 50) {
        ans.resize(50);
    }
    cout << ans.size() << '\n';
    for (auto& i : ans) {
        cout << i.first + 1 << ' ' << i.second + 1 << '\n';
    }




    return 0;
}