#pragma GCC target("avx2")
#pragma GCC optimize("Ofast,unroll-loops")
#include <bits/stdc++.h>
#include <atcoder/all>
#define rep(i, n) for (int i = 0; i < n; i++)
#define per(i, n) for (int i = n - 1; i >= 0; i--)
#define ALL(a) a.begin(), a.end()
typedef long double ldouble;
#undef long
#define long long long
#define vec vector
using namespace std;
using mint = atcoder::modint;
ostream &operator<<(ostream &os, mint a)
{
	return os << a.val();
}
template <typename T>
ostream &operator<<(ostream &os, vector<T> &a)
{
	const int n = a.size();
	rep(i, n)
	{
		os << a[i];
		if (i + 1 != n)
			os << " ";
	}
	return os;
}
template <typename T, size_t n>
ostream &operator<<(ostream &os, array<T, n> &a)
{
	rep(i, n) os << a[i] << " \n"[i + 1 == n];
	return os;
}
template <typename T>
istream &operator>>(istream &is, vector<T> &a)
{
	for (T &i : a)
		is >> i;
	return is;
}
template <typename T>
bool chmin(T &x, T y)
{
	if (x > y)
	{
		x = y;
		return true;
	}
	return false;
}
template <typename T>
bool chmax(T &x, T y)
{
	if (x < y)
	{
		x = y;
		return true;
	}
	return false;
}
void solve()
{
	const auto start = chrono::system_clock::now();
	constexpr int n = 45;
	int muda;
	cin >> muda;
	assert(muda == n);
	array<long, n> a, b;
	rep(i, n) cin >> a[i] >> b[i];
	array<long, n> aa, bb;
	constexpr int m = 50;
	array<int, m> ansu, ansv;
	constexpr long inf = 5e17;
	long ans = 7e18;
	array<int, m> u, v;
	while (true)
	{
		const auto now_time = chrono::system_clock::now();
		const auto elapsed_time = chrono::duration_cast<chrono::milliseconds>(now_time - start).count();
		if (elapsed_time > 900)
			break;
		rep(i, m) u[i] = rand() % n;
		rep(i, m) v[i] = rand() % n;
		rep(i, n)
		{
			aa[i] = a[i];
			bb[i] = b[i];
		}
		rep(i, m)
		{
			aa[u[i]] = aa[v[i]] = (aa[u[i]] + aa[v[i]]) / 2;
			bb[u[i]] = bb[v[i]] = (bb[u[i]] + bb[v[i]]) / 2;
		}
		if (chmin(ans, max(abs(aa[0] - inf), abs(bb[0] - inf))))
		{
			rep(i, m) ansu[i] = u[i];
			rep(i, m) ansv[i] = v[i];
		}
	}
	int x = m;
	rep(i, m) if (ansu[i] == ansv[i]) x--;
	cout << x << '\n';
	rep(i, m) if (ansu[i] != ansv[i]) cout << ansu[i] + 1 << " " << ansv[i] + 1 << '\n';
}
int main()
{
	srand((unsigned)time(NULL));
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	// cout << fixed << setprecision(400);
	int t = 1;
	// cin >> t;
	while (t--)
		solve();
	return 0;
}