#include<iostream>
#include<cstdio>
#include<cstring>

using namespace std;
const int maxn=10010;
bool visit[maxn];
int t,n,cnt,top,_N,f[maxn<<1],d[maxn<<1],p[maxn<<1],next[maxn<<1],h[maxn]={0};
int data[maxn<<1],cou,Log2[maxn<<1],RMQ[19][maxn<<1];
int stack[maxn],num[maxn];
/*struct edgetype
{
	int value;
}edge[maxn];*/
void add(int x,int y)
{
	next[++cnt]=h[x];
	h[x]=cnt;   
	data[cnt]=y;
}
void dfs(int root)
{
	int x,z,y;
	stack[top=1]=root;
	cou=0;
	cnt=1;
	//num[root]=1;
	p[0]=-1;
	while(top)
	{
		x=stack[top];
		cou++;
		if(p[x]==0)p[x]=cou;
		d[cou]=top-1;
		f[cou]=x;
		for(z=h[x];z;z=next[z])
		if(p[y=data[z]]==0)
		{
			//num[y]=++cnt;
			stack[++top]=y;
			break;
		}
		if(z)continue;
		top--;
	}
	_N=cou;	
}
void initrmq()
{
	int i,j,x1,x2,l;
	for(Log2[0]=-1,i=1;i<=_N;i++)
	{
		Log2[i]=(i&(i-1))==0?Log2[i-1]+1:Log2[i-1];
		RMQ[0][i]=i;
	}
	for(j=1,l=2;j<=Log2[_N];l<<=1,j++)
		for(i=1;i+l-1<=_N;i++)
	{
		x1=RMQ[j-1][i];x2=RMQ[j-1][i+(l>>1)];
		RMQ[j][i]=d[x1]<d[x2]?x1:x2;
	}
}
int solve(int aa,int bb)
{
	int x,y,x1,x2,lca,k;
	x=p[aa];
	y=p[bb];
	if(x>y)swap(x,y);
	k=Log2[y-x+1];
	x1=RMQ[k][x];x2=RMQ[k][y-(1<<k)+1];
	lca=f[d[x1]<d[x2]?x1:x2];
	return lca;
}
int main()
{
	int i,j,x,y;
	cin>>t;
	while(t--)
	{
		cin>>n;
		cnt=1;
		memset(visit,true,sizeof(visit));
		memset(h,0,sizeof(h));
		memset(RMQ,0,sizeof(RMQ));
		memset(p,0,sizeof(p));
		memset(d,0,sizeof(d));
		for(i=1;i<n;i++)
		{
			scanf("%d%d",&x,&y);
			visit[y]=false;
			add(x,y);
		}
		for(i=1;i<=n;i++)
		{
			if(visit[i])
			{
				dfs(i);
				break;
			}
		}
		initrmq();
		cin>>x>>y;
		printf("%d\n",solve(x,y));
	}
	return 0;
}