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

vector<int> encode(const vector<vector<int>>& G) {
    int N = (int)G.size();
    vector<int> deg(N);
    priority_queue<int, vector<int>, greater<int>> Q;

    for (int v = 0; v < N; ++v) {
        deg[v] = (int)G[v].size();
        if (deg[v] == 1) Q.push(v);
    }

    vector<int> P;
    for (int i = 0; i < N - 2; ++i) {
        int u = Q.top();
        Q.pop();

        int v = -1;
        for (int w : G[u]) {
            if (deg[w] > 0) {
                v = w;
                break;
            }
        }

        P.push_back(v);
        deg[u] = 0;
        --deg[v];
        if (deg[v] == 1) Q.push(v);
    }
    return P;
}

vector<pair<int, int>> decode(int N, const vector<int>& P) {
    vector<int> cnt(N, 0);
    for (int v : P) ++cnt[v];

    priority_queue<int, vector<int>, greater<int>> Q;
    for (int v = 0; v < N; ++v) {
        if (cnt[v] == 0) Q.push(v);
    }

    vector<pair<int, int>> E;
    for (int i = 0; i < N - 2; ++i) {
        int u = Q.top();
        Q.pop();
        int v = P[i];

        E.emplace_back(u, v);
        --cnt[v];
        if (cnt[v] == 0) Q.push(v);
    }

    int u = Q.top();
    Q.pop();
    int v = Q.top();
    Q.pop();
    E.emplace_back(u, v);
    return E;
}

void Alice() {
    int N;
    cin >> N;
    cout << N - 2 << endl;

    vector<vector<int>> G(N);
    for (int i = 0; i < N - 1; ++i) {
        int u, v;
        cin >> u;
        if (u == -1) return;
        cin >> v;
        if (v == -1) return;

        --u;
        --v;
        G[u].push_back(v);
        G[v].push_back(u);
    }

    vector<int> P = encode(G);
    for (int i = 0; i < N - 2; ++i) {
        if (i) cout << ' ';
        cout << P[i] + 1;
    }
    cout << endl;
}

void Bob() {
    int N;
    cin >> N;
    cout << N - 2 << endl;

    vector<int> P(N - 2);
    for (int& v : P) {
        cin >> v;
        if (v == -1) return;
        --v;
    }

    vector<pair<int, int>> E = decode(N, P);
    for (auto [u, v] : E) {
        cout << u + 1 << ' ' << v + 1 << endl;
    }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    string player;
    cin >> player;
    if (player == "Alice") Alice();
    if (player == "Bob") Bob();
    return 0;
}