#include <bits/stdc++.h>
using namespace std;

//高速化 
struct ponjuice{ponjuice(){cin.tie(0);ios::sync_with_stdio(0);cout<<fixed<<setprecision(20);}}PonJuice;
// #define endl '\n' //インタラクティブ問題の時は消す

//型
using ll = long long;
using ld = long double;

// for文
#define overload4(a, b, c, d, e, ...) e
#define rep1(n)             for(ll i = 0; i < n; i++)
#define rep2(i, n)          for(ll i = 0; i < n; i++)
#define rep3(i, a, b)       for(ll i = a; i < b; i++)
#define rep4(i, a, b, step) for(ll i = a; i < b; i+= step)
#define rep(...) overload4(__VA_ARGS__, rep4, rep3, rep2, rep1)(__VA_ARGS__)
#define per1(n)             for(ll i = n-1; i >= 0; i--)
#define per2(i, n)          for(ll i = n-1; i >= 0; i--)
#define per3(i, a, b)       for(ll i = b-1; i >= a; i--)
#define per4(i, a, b, step) for(ll i = b-1; i >= a; i-= step)
#define per(...) overload4(__VA_ARGS__, per4, per3, per2, per1)(__VA_ARGS__)

//関数
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
template<class S, class T>inline bool chmax(S& a, T b){return a < b && ( a = b , true);}
template<class S, class T>inline bool chmin(S& a, T b){return a > b && ( a = b , true);}

//定数
constexpr ll mod = 998244353;
constexpr ll minf=-(1<<29);
constexpr ll inf=(1<<29);
constexpr ll MINF=-(1LL<<60);
constexpr ll INF=(1LL<<60);
const int dx[4] ={-1, 0, 1, 0};
const int dy[4] ={ 0, 1, 0,-1};
const int dx8[8] ={-1,-1,-1, 0, 1, 1, 1, 0};
const int dy8[8] ={-1, 0, 1, 1, 1, 0,-1,-1};

void solve();
int main() {
	int t = 1;
    // cin >> t;
    while(t--)solve();
}



void alice() {
    ll n;
    cin >> n;
    ll k = n-2;
    cout << k << endl;
    vector<vector<ll>> g(n);
    rep(i,0,n-1 ){
        int a,b;
        cin >> a >> b;
        a--,b--;
        g[a].push_back(b);
        g[b].push_back(a);
    }
    vector<ll> ans;
    
    vector<int> out(n);
    rep(i,0,n) out[i] = g[i].size();
    using S = int;
    priority_queue<S,vector<S>, greater<S>> q;
    rep(i,0,n) if(out[i] == 1) q.push(i);
    while(q.size()) {
        if(ans.size() == k) break;
        auto nw = q.top();
        q.pop();
        for(auto to: g[nw]) {
            if(out[to] > 1) {
                ans.push_back(to+1);
                out[to]--;
                if(out[to] == 1) q.push(to);
            }
        }
    }

    for(auto x: ans) cout << x << " ";cout << endl;
}

#include<atcoder/segtree>
using S = ll;
S op(S a, S b) {return min(a,b);}
S e(){return INF;}
void bob() {
    ll n;
    cin >> n;
    ll k = n-2;
    cout << k << endl;
    vector<ll> a(k);
    rep(i,0,k) cin >> a[i];
    rep(i,0,k) a[i]--;
    
    vector<int> ls(n,-1);
    per(i,0,k) {
        if(ls[a[i]] == -1) ls[a[i]] = i;
    }
    atcoder::segtree<S,op,e> seg(n);
    rep(i,0,n) {
        if(ls[i] == -1) seg.set(i, i);
    }
    rep(i,0,k) {
        ll x = seg.all_prod();
        cout << x+1 << " " << a[i]+1 << endl;
        seg.set(x, INF);
        if(ls[a[i]] == i) seg.set(a[i], a[i]);
    }
    cout << seg.all_prod()+1 << " ";
    seg.set(seg.all_prod(), INF);
    cout << seg.all_prod()+1 << endl;
}

void solve(){
    string s;
    cin >> s;
    if(s == "Alice") alice();
    else bob();
}