import java.io.*;
import java.util.*;
import java.util.function.*;
import java.util.stream.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int m = sc.nextInt();
        int start = sc.nextInt() - 1;
        int goal = sc.nextInt() - 1;
        List<List<Integer>> graph = new ArrayList<>();
        int[] values = new int[n];
        for (int i = 0; i < n; i++) {
            graph.add(new ArrayList<>());
            values[i] = sc.nextInt();
        }
        for (int i = 0; i < m; i++) {
            int a = sc.nextInt() - 1;
            int b = sc.nextInt() - 1;
            graph.get(a).add(b);
            graph.get(b).add(a);
        }
        PriorityQueue<Integer> queue = new PriorityQueue<>((a, b) -> values[b] - values[a]);
        boolean[] visited = new boolean[n];
        queue.add(start);
        int current = values[start];
        int ans = 0;
        while (queue.size() > 0) {
            int idx = queue.poll();
            if (visited[idx]) {
                continue;
            }
            visited[idx] = true;
            if (current > values[idx]) {
                current = values[idx];
                ans++;
            }
            queue.addAll(graph.get(idx));
        }
        System.out.println(ans);
    }
}
class Scanner {
    BufferedReader br;
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() {
        try {
            br = new BufferedReader(new InputStreamReader(System.in));
        } catch (Exception e) {
            
        }
    }
    
    public int nextInt() {
        return Integer.parseInt(next());
    }
    
    public long nextLong() {
        return Long.parseLong(next());
    }
    
    public double nextDouble() {
        return Double.parseDouble(next());
    }
    
    public String next() {
        try {
            while (!st.hasMoreTokens()) {
                st = new StringTokenizer(br.readLine());
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            return st.nextToken();
        }
    }
    
}