use std::{cmp::Reverse, collections::BinaryHeap};

use itertools::Itertools;
use proconio::{input, marker::Usize1};

fn main() {
    input! { player: String }

    if &player == "Alice" {
        alice();
    } else {
        bob();
    }
}

fn alice() {
    input! { n: usize }
    println!("{}", n - 2);

    input! {
        edges: [(Usize1, Usize1); n - 1],
    }

    let mut deg = vec![0; n];
    let mut xor = vec![0; n];
    for &(u, v) in &edges {
        deg[u] += 1;
        deg[v] += 1;
        xor[u] ^= v;
        xor[v] ^= u;
    }

    let mut heap: BinaryHeap<_> = (0..n)
        .filter_map(|v| (deg[v] == 1).then_some(Reverse(v)))
        .collect();

    let mut a = vec![];
    for _ in 0..n - 2 {
        let Reverse(v) = heap.pop().unwrap();
        let u = xor[v];
        deg[u] -= 1;
        xor[u] ^= v;
        if deg[u] == 1 {
            heap.push(Reverse(u));
        }
        a.push(u);
    }

    println!("{}", a.iter().map(|&v| v + 1).join(" "));
}

fn bob() {
    input! { n: usize }
    println!("{}", n - 2);

    input! {
        a: [Usize1; n - 2],
    }

    let mut cnt = vec![0; n];
    for &a in &a {
        cnt[a] += 1;
    }

    let mut heap: BinaryHeap<_> = (0..n)
        .filter_map(|v| (cnt[v] == 0).then_some(Reverse(v)))
        .collect();

    let mut edges = vec![];
    for &v in &a {
        let Reverse(u) = heap.pop().unwrap();
        cnt[v] -= 1;
        if cnt[v] == 0 {
            heap.push(Reverse(v));
        }
        edges.push((u, v));
    }

    let Reverse(u) = heap.pop().unwrap();
    let Reverse(v) = heap.pop().unwrap();
    edges.push((u, v));

    for &(u, v) in &edges {
        println!("{} {}", u + 1, v + 1);
    }
}