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 plan = 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();
        plan.push((x, y));
    }

    let target = 10_i64.pow(17) * 5;
    let mut ans = vec![];
    for i in 0..50 {
        let mut min_diff = 0;
        let mut tmp = (n, n);
        for p in 0..n {
            for q in p + 1..n {
                let prev_diff = max((plan[p].0 - target).abs(), (plan[q].0 - target).abs()) + max((plan[p].1 - target).abs(), (plan[q].1 - target).abs());
                let new_0 = (plan[p].0 + plan[q].0) / 2;
                let new_1 = (plan[p].1 + plan[q].1) / 2;
                let new_diff = (new_0 - target).abs() + (new_1 - target).abs();
                if(min_diff > new_diff - prev_diff) {
                    min_diff = new_diff - prev_diff;
                    tmp = (p, q);
                }
            }
        }
        if min_diff == 0 {
            break;
        }
        plan[tmp.0].0 = (plan[tmp.0].0 + plan[tmp.1].0) / 2;
        plan[tmp.1].0 = (plan[tmp.0].0 + plan[tmp.1].0) / 2;
        plan[tmp.0].1 = (plan[tmp.0].1 + plan[tmp.1].1) / 2;
        plan[tmp.1].1 = (plan[tmp.0].1 + plan[tmp.1].1) / 2;
        ans.push(tmp);
    }
    println!("{}", ans.len());
    for a in ans {
        println!("{} {}", a.0 + 1, a.1 + 1);
    }
}