use std::cmp::{max, min};
use std::io;



fn main() {
    let mut buffer = String::new();
    io::stdin().read_line(&mut buffer).unwrap();
    let n: usize = buffer.trim().parse().unwrap();
    let mut cards = vec![];
    for _ in 0..n {
        let mut buffer = String::new();
        io::stdin().read_line(&mut buffer).unwrap();
        let mut iter = buffer.trim().split_whitespace();
        let x: i64 = iter.next().unwrap().parse().unwrap();
        let y: i64 = iter.next().unwrap().parse().unwrap();
        cards.push((x, y));
    }

    let target = 10_i64.pow(17) * 5;
    let mut ans = vec![];
    for i in 0..50 {
        let mut cur_diff = max((cards[0].0 - target).abs(), (cards[0].1 - target).abs());
        let mut tmp = (n, n);
        for p in 1..n {
            let new_card_0 = ((cards[p].0 + cards[0].0) / 2, (cards[p].1 + cards[0].1) / 2);
            let new_diff = max((new_card_0.0 - target).abs(), (new_card_0.1 - target).abs());
            if new_diff < cur_diff {
                cur_diff = new_diff;
                tmp = (0, p);
            }
        }
        if i < 49 {
            for p in 1..n {
                for q in p + 1..n {
                    let new_card = ((cards[p].0 + cards[q].0) / 2, (cards[p].1 + cards[q].1) / 2);

                    let new_card_0 = ((cards[0].0 + new_card.0) / 2, (cards[0].1 + new_card.1) / 2);
                    let new_diff = max((new_card_0.0 - target).abs(), (new_card_0.1 - target).abs());
                    if new_diff < cur_diff {
                        cur_diff = new_diff;
                        tmp = (p, q);
                    }
                }
            }
        }
        if tmp == (n, n) {
            break;
        }
        let new_card = ((cards[tmp.0].0 + cards[tmp.1].0) / 2, (cards[tmp.0].1 + cards[tmp.1].1) / 2);
        cards[tmp.0] = new_card;
        cards[tmp.1] = new_card;
        ans.push(tmp);
    }
    println!("{}", ans.len());
    for a in ans {
        println!("{} {}", a.0 + 1, a.1 + 1);
    }
    // eprintln!("{:?}", cards);
}