package com.company;
import java.util.HashMap;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int numCases = sc.nextInt();

        for(int i = 0; i < numCases; i ++ ){
            int numNodes = sc.nextInt();

            HashMap<Integer,Integer> Tree = new HashMap<Integer, Integer>();
            for(int j = 0; j < numNodes - 1; j ++){
                int parent = sc.nextInt();
                int child = sc.nextInt();

                Tree.put(child, parent);
            }

            int num1 = sc.nextInt();
            int num2 = sc.nextInt();

            HashMap<Integer, Integer> backTrack = new HashMap<Integer,Integer>();

            Integer currentNode = num1;
            while( Tree.containsKey( currentNode ) ){
                backTrack.put(currentNode, Tree.get(currentNode));
                currentNode = Tree.get(currentNode);
            }

            currentNode = num2;
            while( Tree.containsKey( currentNode ) ){
                if(backTrack.containsKey(currentNode)){
                    break;
                }
                currentNode = Tree.get(currentNode);
            }

            System.out.println(currentNode);
        }
    }
}