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

#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define rrep(i,n) for(int i=(int)(n-1);i>=0;i--)
#define ALL(v) v.begin(),v.end()
#define RALL(v) v.rbegin(),v.rend()
template <class T> using V=vector<T>;
template <class T> using VV=V<V<T>>;
using u128=__int128_t;
using ll=long long;

V<int> PruferEncode(VV<int>& G){
  int n=G.size();
  V<int> ret,deg(n);
  rep(v,n) deg[v]=G[v].size();
  
  priority_queue<int,V<int>,greater<int>> que;
  rep(v,n) if(deg[v]==1) que.push(v);
  
  rep(i,n-2){
    auto u=que.top(); que.pop();
    int v;
    for(auto nv:G[u]){
      if(deg[nv]){
        v=nv;
        break;
      }
    }
    ret.push_back(v);
    deg[u]=0;
    deg[v]--;
    if(deg[v]==1) que.push(v);
  }
  return ret;
}

V<pair<int,int>> PruferDecode(V<int>& P){
  int n=P.size()+2;
  V<int> cnt(n);
  for(auto v:P) cnt[v]++;
  
  priority_queue<int,V<int>,greater<int>> que;
  rep(v,n) if(cnt[v]==0) que.push(v);
  
  V<pair<int,int>> ret;
  rep(i,n-2){
    auto u=que.top(); que.pop();
    int v=P[i];
    ret.push_back(make_pair(u,v));
    cnt[v]--;
    if(cnt[v]==0) que.push(v);
  }
  auto u=que.top(); que.pop();
  auto v=que.top(); que.pop();
  ret.push_back(make_pair(u,v));
  return ret;
}
 
int main(){
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  
  string s;
  int n;
  cin>>s>>n;
  cout<<n-2<<endl;
  if(s=="Alice"){
    VV<int> G(n);
    rep(i,n-1){
      int u,v;
      cin>>u>>v;
      u--,v--;
      G[u].push_back(v);
      G[v].push_back(u);
    }
    auto P=PruferEncode(G);
    rep(i,n-2){
      if(i) cout<<" ";
      cout<<P[i]+1;
    }
    cout<<endl;
  }
  else{
    V<int> P(n-2);
    rep(i,n-2){
      cin>>P[i];
      P[i]--;
    }
    auto G=PruferDecode(P);
    rep(i,n-1) cout<<G[i].first+1<<" "<<G[i].second+1<<endl;
  }
  
  return 0;
}