#include "stdafx.h"
#include <stdio.h>
#include <string.h>
#include<fstream>
#include <iostream>
#include <queue>
#include <deque>
#include <vector>
using namespace std;

struct vertex
{
	vector<int> edges;
	bool visited;
};

int dist = 0;

int BFS(vertex Graph[], int v, int target) {
	deque<int> Q;
	Q.push_front(v);
	Graph[v].visited = true;
	while (!Q.empty()) {
		int t = Q.back();
		Q.pop_back();
		if (t == target) {
			return t;
		}
		for (unsigned int i = 0; i < Graph[t].edges.size(); i++) {
			int u = Graph[t].edges[i];
			if (!Graph[u].visited) {
				Graph[u].visited = true;
				Q.push_front(u);
			}
		}
	}
	return -1;
}

int main()
{
	ifstream in("matrix.txt");
	int n=7;
	//cin >> n;
	vertex Graph[7];
	int k;
	//cin >> k;
	for (int i = 0; i < 9; i++)
	{
		int a, b;
		in >> a >> b;
		a--;
		b--;
		Graph[a].edges.push_back(b);
		Graph[b].edges.push_back(a);
	}

	for (int i = 0; i < n; i++) {
		Graph[i].visited = false;
	}

	int s, t;
	cin >> s >> t;

	cout << BFS(Graph, s, t);

}