#include <bits/stdc++.h>
#define fi first
#define se second
#define rep(i,s,n) for (int i = (s); i < (n); ++i)
#define rrep(i,g,n) for (int i = (n)-1; i >= (g); --i)
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define len(x) (int)(x).size()
#define dup(x,y) (((x)+(y)-1)/(y))
#define pb push_back
#define eb emplace_back
#define Field(T) vector<vector<T>>
using namespace std;
using ll = long long;
using ull = unsigned long long;
template<typename T> using pq = priority_queue<T,vector<T>,greater<T>>;
using P = pair<int,int>;
template<class T>bool chmax(T&a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T>bool chmin(T&a,T b){if(b<a){a=b;return 1;}return 0;}

void alice() {
  int n;
  cin >> n;
  cout << n-2 << endl;
  vector<int> u(n), v(n);
  vector<vector<int>> G(n);
  rep(i,0,n-1) {
    cin >> u[i] >> v[i];
    --u[i], --v[i];
    G[u[i]].eb(v[i]), G[v[i]].eb(u[i]);
  }
  vector<int> a(n-2);
  rep(i,0,n-2) {
    rep(v,0,n) {
      if (len(G[v]) == 1) {
        a[i] = G[v][0];
        G[a[i]].erase(find(all(G[a[i]]), v));
        G[v].clear();
        break;
      }
    }
  }
  rep(i,0,n-2) {
    cout << a[i]+1 << " ";
  }
  cout << endl;
}

void bob() {
  int n;
  cin >> n;
  cout << n-2 << endl;
  vector<int> a(n-2);
  rep(i,0,n-2) cin >> a[i], --a[i];
  vector<int> d(n, 1);
  rep(i,0,n-2) ++d[a[i]];
  rep(i,0,n-2) {
    rep(j,0,n) {
      if (d[j] == 1) {
        cout << a[i]+1 << " " << j+1 << endl;
        --d[a[i]], --d[j];
        break;
      }
    }
  }
  int u = -1, v = -1;
  rep(i,0,n) {
    if (d[i] == 1) {
      if (u == -1) u = i;
      else v = i;
    }
  }
  cout << u+1 << " " << v+1 << endl;
}

int main() {
  string s;
  cin >> s;
  if (s[0] == 'A') alice();
  else bob();
  return 0;
}