/* ***********************************************

 Author        :kuangbin

 Created Time  :2013-9-5 9:45:17

 File Name     :F:\2013ACM练习\专题学习\LCA\POJ1330_3.cpp

 ************************************************ */

 #include <stdio.h>

 #include <string.h>

 #include <iostream>

 #include <algorithm>

 #include <vector>

 #include <queue>

 #include <set>

 #include <map>

 #include <string>

 #include <math.h>

 #include <stdlib.h>

 #include <time.h>

 using namespace std;

 /*

 * POJ 1330

 * LCA 在线算法

 */

 const int MAXN = ;

 const int DEG = ;

 struct Edge

 {

     int to, next;

 }edge[MAXN * ];

 int head[MAXN], tot;

 void addedge(int u, int v)

 {

     edge[tot].to = v;

     edge[tot].next = head[u];

     head[u] = tot++;

 }

 void init()

 {

     tot = ;

     memset(head, -, sizeof(head));

 }

 int fa[MAXN][DEG];//fa[i][j]表示结点i的第2^j个祖先

 int deg[MAXN];//深度数组

 void BFS(int root)

 {

     queue<int>que;

     deg[root] = ;

     fa[root][] = root;

     que.push(root);

     while (!que.empty())

     {

         int tmp = que.front();

         que.pop();

         for (int i = ; i < DEG; i++)

             fa[tmp][i] = fa[fa[tmp][i - ]][i - ];

         for (int i = head[tmp]; i != -; i = edge[i].next)

         {

             int v = edge[i].to;

             if (v == fa[tmp][])continue;

             deg[v] = deg[tmp] + ;

             fa[v][] = tmp;

             que.push(v);

         }

     }

 }

 int LCA(int u, int v)

 {

     if (deg[u] > deg[v])swap(u, v);

     int hu = deg[u], hv = deg[v];

     int tu = u, tv = v;

     for (int det = hv - hu, i = ; det; det >>= , i++)

     if (det & )

         tv = fa[tv][i];

     if (tu == tv)return tu;

     for (int i = DEG - ; i >= ; i--)

     {

         if (fa[tu][i] == fa[tv][i])

             continue;

         tu = fa[tu][i];

         tv = fa[tv][i];

     }

     return fa[tu][];

 }

 bool flag[MAXN];

 int main()

 {

     freopen("in.txt","r",stdin);

     //freopen("out.txt","w",stdout);

     int T;

     int n;

     int u, v;

     scanf("%d", &T);

     while (T--)

     {

         scanf("%d", &n);

         init();

         memset(flag, false, sizeof(flag));

         for (int i = ; i < n; i++)

         {

             scanf("%d%d", &u, &v);

             addedge(u, v);

             addedge(v, u);

             flag[v] = true;

         }

         int root;

         for (int i = ; i <= n; i++)

         if (!flag[i])

         {

             root = i;

             break;

         }

         BFS(root);

         scanf("%d%d", &u, &v);

         printf("%d\n", LCA(u, v));

     }

     return ;

 }