#include <bits/stdc++.h>   using namespace std;   int64_t dfs(int64_t idx, int64_t p, vector<vector<int64_t>>& g,               vector<int64_t>& parents, int64_t& c1, int64_t& c2) {     int64_t n = g.size() - 1;     parents[idx] = p;     int64_t res = 1;     int64_t mx = 0;     for (auto& x : g[idx]) {       if (x != p) {         int64_t a = dfs(x, idx, g, parents, c1, c2);         res += a;         mx = max(mx, a);       }     }     mx = max(mx, n - res);     if (mx <= n / 2) {       if (c1 == -1) {         c1 = idx;       } else {         c2 = idx;       }     }     return res;   }   int64_t leaf(int64_t idx, int64_t p, vector<vector<int64_t>>& g) {     if (g[idx].size() == 1) {       return idx;     } else {       auto res = -1;       for (auto& e : g[idx]) {         if (e != p) {           res = leaf(e, idx, g);           if (res != -1) {             return res;           }         }       }     }     return -1;   }   int main() {     ios::sync_with_stdio(false);     cin.tie(0);     cout.tie(0);     int64_t tc;     cin >> tc;     while (tc--) {       int64_t n;       cin >> n;       vector<vector<int64_t>> g(n + 1);       for (int64_t i = 0; i < n - 1; i++) {         int64_t a;         int64_t b;         cin >> a >> b;         g[a].push_back(b);         g[b].push_back(a);       }       int64_t c1 = -1;       int64_t c2 = -1;       vector<int64_t> p(n + 1);       dfs(1, 0, g, p, c1, c2);       if (c2 == -1) {         int64_t rm = g[c1][0];         cout << c1 <<     << rm << endl;         cout << c1 <<     << rm << endl;       } else {         if (p[c2] != c1) {           swap(c1, c2);         }         int64_t rm = leaf(c2, c1, g);         cout << rm <<     << p[rm] << endl;         cout << rm <<     << c1 << endl;       }     }     return 0;   }   