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, we will be given at max 1 node with zero val
another twist is the initial zero node is infected ,it can spread its virus to nodes near to k levels
now find the shortest distance between source node and destination node
 */
/**
 important point to understand here -

you need to find the graph after the infection has been spread and then think about the shortest distance


 */
 /*

//inputs for visitable and graph and N and infectedNode and k
1 1 1 1 1 1 1 1 1 1 1 1 1 1
14 17
0 1
0 5
1 2
5 6
2 3
6 7
6 12
3 7
3 4
7 8
12 13
8 4
13 9
9 10
10 8
10 11
11 4
11
3
1

expected output -
The result is 7


 */


@SuppressWarnings({"unused","unchecked"})
public class A20250208b_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);
        }
        //lets spoil the visitability by spreading infection
        int n = getArray()[0];
        int infectedNode = getArray()[0];
        int k = getArray()[0];

        int[] visited;
        int[] level;
        Queue<Integer> q;
        //assign new values for v l q
        visited = new int[nodes];
        level = new int[nodes];
        Arrays.fill(level,-2);
        q = new LinkedList<>();


        visited[infectedNode] = 1;
        visitable[infectedNode] = 0;
        level[infectedNode] = 0;
        q.offer(infectedNode);

        while(!q.isEmpty()){
            int parent = q.poll();
            if(level[parent]==k){
                continue;//you dont need further infection spread
            }
            for(int child:adjList[parent]){
                if(visitable[child]==1 && visited[child] == 0){
                    visitable[child] = 0;
                    visited[child] = 1;
                    level[child] = level[parent]+1;
                    q.offer(child);
                }
            }
        }


        //assign new values for v l q after infection
        visited = new int[nodes];
        level = new int[nodes];
        Arrays.fill(level,-2);
        q = new LinkedList<>();

        if(visitable[0] == 1){
            visited[0] = 1;
            level[0] = 0;
            q.offer(0);
        }

        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);
                }
            }
        }

        int res = level[n];


        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;

    }
}