#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using llu = long long unsigned;

vector<ll> dx = { 0, 0, -1, 1};
vector<ll> dy = {-1, 1,  0, 0};

#define TARGET 500000000000000000LL 
ll scoreCal(ll a0, ll a1, ll b0, ll b1) {
    ll newA = (a0 + a1) / 2;
    ll newB = (b0 + b1) / 2;
    ll score = max( abs(TARGET-newA), abs(TARGET-newB));
    return score;
}

int main() {
    int N;
    cin >> N;
    vector<ll> A(N), B(N);
    for (int i=0; i<N; ++i) {
        cin >> A[i] >> B[i];
    }

    vector<pair<int, int>> ret;
    for (int i=0; i<50; ++i) {
        int u = 0;
        int v = 0;
        ll minScore = scoreCal(A[0], A[0], B[0], B[0]);
        //cout << "1 - 1 minScore = " << minScore << endl;
        for (int j=1; j<N; ++j) {
            ll score = scoreCal(A[0], A[j], B[0], B[j]);
            //cout << "1 - " << j+1 << " minScore = " << score << endl;
            if (score < minScore) {
                minScore = score;
                v = j;
            }
        }
        if (v == 0) {
            if (abs(A[0]-TARGET) > abs(B[0]-TARGET)) {
                if (A[0]>TARGET) {
                    // Aを小さくしたい
                    int min1 = 1;
                    int min2 = 2;
                    ll minV1 = A[min1];
                    ll minV2 = A[min2];
                    for (int j=3; j<N; ++j) {
                        if (A[j] < minV1) {
                            minV1 = A[j];
                            min1 = j;
                            continue;
                        }
                        if (A[j] < minV2) {
                            minV2 = A[j];
                            min2 = j;
                        }
                    }
                    u = min1;
                    v = min2;
                } else {
                    // Aを大きくしたい
                    int max1 = 1;
                    int max2 = 2;
                    ll maxV1 = A[max1];
                    ll maxV2 = A[max2];
                    for (int j=3; j<N; ++j) {
                        if (maxV1 < A[j]) {
                            maxV1 = A[j];
                            max1 = j;
                            continue;
                        }
                        if (maxV2 < A[j]) {
                            maxV2 = A[j];
                            max2 = j;
                        }
                    }
                    u = max1;
                    v = max2;
                }
            } else {
                if (B[0]>TARGET) {
                    // Bを小さくしたい
                    int min1 = 1;
                    int min2 = 2;
                    ll minV1 = B[min1];
                    ll minV2 = B[min2];
                    for (int j=3; j<N; ++j) {
                        if (B[j] < minV1) {
                            minV1 = B[j];
                            min1 = j;
                            continue;
                        }
                        if (B[j] < minV2) {
                            minV2 = B[j];
                            min2 = j;
                        }
                    }
                    u = min1;
                    v = min2;
                } else {
                    // Bを大きくしたい
                    int max1 = 1;
                    int max2 = 2;
                    ll maxV1 = B[max1];
                    ll maxV2 = B[max2];
                    for (int j=3; j<N; ++j) {
                        if (maxV1 < B[j]) {
                            maxV1 = B[j];
                            max1 = j;
                            continue;
                        }
                        if (maxV2 < B[j]) {
                            maxV2 = B[j];
                            max2 = j;
                        }
                    }
                    u = max1;
                    v = max2;                    
                }
            }
        }
        ret.push_back(make_pair(u+1, v+1));
        //cout << "1 - " << v+1 << " execute" << endl; 
        ll newA = (A[u] + A[v]) / 2;
        ll newB = (B[u] + B[v]) / 2;
        A[u] = A[v] = newA;
        B[u] = B[v] = newB;
        //for (int i=0; i<N; ++i) { cout << A[i] << " " << B[i] << endl; }
    }

    cout << ret.size() << endl;
    for (auto x : ret) {
        cout << x.first << " " << x.second << endl;
    }
    return 0;
}