use proconio::input;

fn main(){
    input!{
        n: usize,
        a: [i64; 2*n],
    }

    let mut b = Vec::<(i64, usize)>::new();
    for i in 0..2*n{
        b.push((a[i], i+1));
    }
    b.sort();

    let l = &b[..n];
    let r = &b[n..];
    let mut ans: i64 = 0;
    for i in 0..n{
        ans += (l[i].0-r[n-i-1].0).abs();
    }

    println!("{}", ans);
    for i in 0..n{
        println!("{} {}", l[i].1, r[n-i-1].1);
    }
}