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

 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 ;

 }