import java.io.*;
import java.util.*;
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 s = sc.nextInt() - 1;
        int t = sc.nextInt() - 1;
        City[] cities = new City[n];
        ArrayList<ArrayList<City>> graph = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            cities[i] = new City(i, sc.nextInt());
            graph.add(new ArrayList<>());
        }
        for (int i = 0; i < m; i++) {
            int a = sc.nextInt() - 1;
            int b = sc.nextInt() - 1;
            graph.get(a).add(cities[b]);
            graph.get(b).add(cities[a]);
        }
        TreeSet<City> nextTo = new TreeSet<>();
        int current = cities[s].value;
        nextTo.addAll(graph.get(s));
        HashSet<Integer> visited = new HashSet<>();
        visited.add(s);
        int ans = 0;
        while (nextTo.size() > 0) {
            City y = nextTo.pollLast();
            if (visited.contains(y.idx)) {
                continue;
            }
            visited.add(y.idx);
            if (y.value < current) {
                ans++;
                current = y.value;
            }
            nextTo.addAll(graph.get(y.idx));
        }
        System.out.println(ans);
    }
    
    static class City implements Comparable<City> {
        int idx;
        int value;
        
        public City(int idx, int value) {
            this.idx = idx;
            this.value = value;
        }
        
        public int compareTo(City another) {
            if (value == another.value) {
                return idx - another.idx;
            } else {
                return value - another.value;
            }
        }
        
        public int hashCode() {
            return idx;
        }
        
        public boolean equals(Object o) {
            City x = (City)o;
            return x.idx == idx;
        }
    }
}
class Utilities {
    static String arrayToLineString(Object[] arr) {
        return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n"));
    }
    
    static String arrayToLineString(int[] arr) {
        return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new));
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public int[] nextIntArray() throws Exception {
        return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
    
}