func_code_string: #include <bits/stdc++.h>   using namespace std;   int ask(string q, int x) {     cout << q <<     << x << endl;     int ret;     cin >> ret;     return ret;   }   int getclosestnode(vector<vector<int>> &adj, set<int> &me, int node) {     bool visited[1001];     memset(visited, 0, sizeof visited);     queue<int> q;     q.push(node);     while (!q.empty()) {       int u = q.front();       q.pop();       if (me.count(u) != 0)         return u;       else         for (auto x : adj[u])           if (!visited[x]) {             q.push(x);             visited[x] = 1;           }     }     return -1;   }   void solve() {     int n;     vector<vector<int>> adj(1001);     cin >> n;     for (int i = 0; i < (int)(n - 1); i++) {       int a, b;       cin >> a >> b;       adj[a].push_back(b);       adj[b].push_back(a);     }     set<int> me, li;     int k;     cin >> k;     for (int i = 0; i < (int)(k); i++) {       int a;       cin >> a;       me.insert(a);     }     cin >> k;     for (int i = 0; i < (int)(k); i++) {       int a;       cin >> a;       li.insert(a);     }     int node = ask( B , *li.begin());     if (me.count(node) != 0)       cout <<  C   << node << endl;     else {       int closest = getclosestnode(adj, me, node);       int liclose = ask( A , closest);       if (li.count(liclose) != 0) {         cout <<  C   << closest << endl;       } else         cout <<  C   << -1 << endl;     }   }   int main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     int tc;     cin >> tc;     for (int i = 0; i < (int)(tc); i++) solve();     return 0;   }   