#include <bits/stdc++.h>
using namespace std;

int main() {
	// step #1. input
	int N;
	cin >> N;
	vector<double> A(N), B(N);
	for (int i = 0; i < N; i++) {
		cin >> A[i] >> B[i];
		A[i] -= 5.0e+17;
		B[i] -= 5.0e+17;
	}
	
	// step #2. choose pairing with (A[0], B[0])
	double basebest = 1.0e+99;
	int basechoice = 0;
	for (int i = 1; i < N; i++) {
		double d = max(abs((A[0] + A[i]) / 2), abs((B[0] + B[i]) / 2));
		if (basebest > d) {
			basebest = d;
			basechoice = i;
		}
	}
	
	// step #3. construction
	double x = (A[0] + A[basechoice]) * 0.25;
	double y = (B[0] + B[basechoice]) * 0.25;
	vector<bool> used(N, false);
	used[0] = true;
	used[basechoice] = false;
	vector<int> track = { 0 };
	for (int level = 2; level <= N - 1; level++) {
		double mul = pow(0.5, level != N - 1 ? level : N - 2);
		double best = 1.0e+99;
		int pos = -1;
		for (int j = 0; j < N; j++) {
			if (!used[j]) {
				double d = max(abs(x + A[j] * mul), abs(y + B[j] * mul));
				if (best > d) {
					best = d;
					pos = j;
				}
			}
		}
		used[pos] = true;
		x += A[pos] * mul;
		y += B[pos] * mul;
		track.push_back(pos);
		cerr << "level = " << level << ": best = " << best << endl;
	}
	
	// step #3. output
	cout << N - 1 << endl;
	cout << 0 + 1 << ' ' << basechoice + 1 << endl;
	for (int i = N - 3; i >= 0; i--) {
		cout << track[i] + 1 << ' ' << track[i + 1] + 1 << endl;
	}
	
	return 0;
}