func_code_string: #include <bits/stdc++.h>   using namespace std;   int n, k1, k2, u[1001], q[1001], start, x, y;   vector<int> vec[1001];   int a, b;   int f(int v, int pr) {     if (u[v] == 1) {       return v;     }     int yy = 0;     for (int i = 0; i < vec[v].size(); i++) {       if (vec[v][i] != pr) {         yy = max(yy, f(vec[v][i], v));       }     }     return yy;   }   pair<int, int> get(int v, int pr) {     pair<int, int> ans = make_pair(0, 0);     if (v == y) {       ans.first = 1;       return ans;     }     if (u[v] == 1) {       ans.second = v;     }     pair<int, int> yy = make_pair(0, 0);     for (int i = 0; i < vec[v].size(); i++) {       if (vec[v][i] != pr) {         yy = max(yy, get(vec[v][i], v));       }     }     if (yy.first != 0) {       ans.first = 1;     }     if (yy.first != 0 && yy.second != 0) {       ans = yy;     }     return ans;   }   void solve() {     for (int i = 0; i < 1001; i++) {       vec[i].clear();       u[i] = 0;       q[i] = 0;     }     cin >> n;     for (int i = 1; i < n; i++) {       scanf( %d%d , &a, &b);       vec[a].push_back(b);       vec[b].push_back(a);     }     cin >> k1;     for (int i = 0; i < k1; i++) {       scanf( %d , &x);       u[x] = 1;     }     cin >> k2;     for (int i = 0; i < k2; i++) {       scanf( %d , &x);       q[x] = 1;     }     start = f(1, -1);     cout <<  A   << start << endl;     fflush(stdout);     cin >> y;     if (q[y] == 1) {       cout <<  C   << start << endl;       fflush(stdout);       return;     } else {       cout <<  B   << x << endl;       fflush(stdout);       cin >> y;       if (u[y] == 1) {         cout <<  C   << y << endl;         fflush(stdout);         return;       } else {         pair<int, int> ppp = get(1, -1);         if (ppp.second == 0) {           cout <<  C -1  << endl;           fflush(stdout);           return;         }         start = ppp.second;         cout <<  A   << start << endl;         fflush(stdout);         cin >> y;         if (q[y] == 1) {           cout <<  C   << start << endl;           fflush(stdout);           return;         } else {           cout <<  C -1  << endl;           fflush(stdout);           return;         }       }     }   }   int main() {     int test;     cin >> test;     while (test--) {       solve();     }     return 0;   }   