func_code_string: #include <bits/stdc++.h>   using namespace std;   using lli = long long;   using lld = long double;   using ulli = unsigned long long int;   using pll = pair<lli, lli>;   using ttt = pair<lli, pll>;   using vttt = vector<ttt>;   using vll = vector<pll>;   using vl = vector<lli>;   using vi = vector<int>;   using vvi = vector<vector<int>>;   using cd = complex<lld>;   const double PI = acos(-1);   vvi adj, dist;   pll get(vi vect) {     cout <<  ?   << ((lli)(vect).size());     for (auto& x : vect) cout <<     << x;     cout <<   n ;     cout.flush();     pll ans;     cin >> ans.first >> ans.second;     return ans;   }   void dfs(int v, int p, int dis) {     dist[dis].push_back(v);     for (auto& x : adj[v])       if (x != p) {         dfs(x, v, dis + 1);       }   }   pll check(int val) {     if (dist[val].empty()) return {1000000007, 1000000007};     return get(dist[val]);   }   int tejas_919(int kkkk) {     lli n, m, k, q, u, v, temp = 0, ans = 0;     cin >> n;     adj = vvi(n + 2);     dist = vvi(n + 2);     for (int i = 1; i < n; i++) {       cin >> u >> v;       adj[u].push_back(v);       adj[v].push_back(u);     }     int root, pdist;     {       vi vect;       for (int i = 1; i < n + 1; i++) vect.push_back(i);       tie(root, pdist) = get(vect);     }     dfs(root, root, 0);     int l = (pdist + 1) / 2, r = pdist, cdis;     root = -1;     while (l <= r) {       int mid = (l + r) / 2;       tie(temp, cdis) = check(mid);       if (cdis == pdist) {         l = mid + 1;         root = temp;       } else         r = mid - 1;     }     if (root < 0) root = get(dist[l - 1]).first;     dist = vvi(n + 2);     dfs(root, root, 0);     ans = get(dist[pdist]).first;     cout <<  !   << root <<     << ans <<   n ;     cout.flush();     string s;     cin >> s;     return 0;   }   signed main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     cout.tie(NULL);     cout << fixed << setprecision(10);     int t = 1;     cin >> t;     for (int i = 0; i < t; i++) {       tejas_919(i + 1);     }     {};   }   