import java.util.*;

/*

given a connected undirectional unweighted graph
you need to find the shortest distance between source node and destination node
twist is you can only travel if they are having visitable as 1

 */
/**
 important point to understand here -

you can do a simple bfs , but you will visit the nodes only if they are visitable
otherwise no

 */
 /*

//inputs for visitable and graph
1 1 0 1 1
5 5
0 1
0 2
1 3
2 4
3 4
4

expected output -
The result is 3


 */


@SuppressWarnings({"unused","unchecked"})
public class A20250208a_atlassianOA  {

    static Scanner sc = new Scanner(System.in);

    private static int[] getArray() {
        String[] sArr = sc.nextLine().split(" ");
        int[] arr = Arrays.stream(sArr).mapToInt(Integer::parseInt).toArray();
        return arr;
    }

    private static char[] getCharArray() {
        String[] sArr = sc.nextLine().split(" ");
        char[] cArr = new char[sArr.length];
        for (int i = 0; i < sArr.length; i++) {
            cArr[i] = sArr[i].charAt(0); // Take the first character of each string
        }
        return cArr;
    }

    private static int getMax(int[] arr) {
        int currMax = Integer.MIN_VALUE;
        for (int curr : arr) {
            currMax = Math.max(currMax, curr);
        }
        return currMax;
    }

    public static void main(String args[]) {
        // prepare the inputs


        int[] visitable = getArray();
        int[] tempArr = getArray();

        int nodes = tempArr[0];
        int edges = tempArr[1];
        ArrayList<Integer>[] adjList =(ArrayList<Integer>[]) new ArrayList[nodes];//explicit type conversion
        for(int i =0;i<nodes;i+=1){
            adjList[i] = new ArrayList<>();
        }
        int temp = edges;
        //fill up the graph
        while(temp!=0){
            temp-=1;
            tempArr = getArray();
            int n1 = tempArr[0];
            int n2 = tempArr[1];
            adjList[n1].add(n2);
            adjList[n2].add(n1);
        }

        Queue<Integer> q = new LinkedList<>();
        int[] level = new int[nodes];
        Arrays.fill(level,(int)1e8);//filling level with some big number
        int[] visited = new int[nodes];

        if(visitable[0]==1){
            visited[0] = 1;
            level[0] = 0;
            q.offer(0);//offer is safe than add
        }

        while(!q.isEmpty()){
            int parent = q.poll();
            for(int child:adjList[parent]){
                if(visitable[child]==1 && visited[child]==0){
                    visited[child]=1;
                    level[child] = level[parent]+1;
                    q.offer(child);
                }
            }
        }
        tempArr = getArray();
        int res = level[tempArr[0]];

        System.out.println("The result is " + res);

    }
}

class Pair{
    int row;
    int col;
    public Pair(int i,int j){
        this.row = i;
        this.col = j;

    }
}