#include<stdio.h>
#include<cstdlib>
#include<iostream>
#include<cstdio>
#include<vector>
#include<cstring>
#include<stack>
#include<queue>
using namespace std;
typedef long long LL;
int par[10010];//父親
int ra[10010], rb[10010];
queue<int>road;

void init(int n) {
	for (int i = 0; i <= n; i++) {
		par[i]=i;
	}
}

int Find1(int x) { //不需要記錄路徑的查詢
	if (par[x] == x)return x;
	else {
		return Find1(par[x]);
	}
}

int Find(int x) {  //需要記錄路徑的查詢
	road.push(x);
	if (par[x] == x)return x;
	else {
		return Find(par[x]);
	}
}

void unite(int a, int b) {
	if (Find1(a) == Find1(b))return;
	par[b] = a; //不能按照並查集那樣合併  find也不需要壓縮路徑
}

int main() {
	int Case;
	scanf_s("%d", &Case);
	while (Case--) {
		int n; scanf_s("%d", &n);
		init(n);
		for (int i = 0; i < n - 1; i++) {
			int a, b;
			scanf_s("%d%d", &a, &b);
			unite(a, b);
		}//建立並查集
		int a, b;
		scanf_s("%d%d", &a, &b);
		int ia = -1, ib = -1;
		while (!road.empty())road.pop();
		Find(a);
		while (!road.empty()) {
			ra[++ia] = road.front();
			road.pop();
		}//路程放入陣列
		Find(b);
		while (!road.empty()) {
			rb[++ib] = road.front();
			road.pop();
		}//路程放入陣列
		while (ia >= 0 && ib >= 0) {
			if (ra[ia] == rb[ib]) { ia--; ib--; }
			else { printf("%d\n", ra[ia + 1]); break; }
		}
		if (ia < 0)printf("%d\n", rb[ib + 1]);
		else if (ib < 0)printf("%d\n", ra[ia + 1]);
	}
}