#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
vector<vector<int>> vec(100010);
bool b[100010] = { false };
int b1[100010];
int p[100010];
int main() {
	int n, m, s, t;
	cin >> n >> m >> s >> t;
	for (int i = 1; i <= n; i++) {
		cin >> p[i];
		b1[i] = p[i];
	}
	for (int i = 0; i < m; i++) {
		int a, b;
		cin >> a >> b;
		vec[a].emplace_back(b);
		vec[b].emplace_back(a);
	}
	priority_queue<pair<int, int>> que;
	que.push(make_pair(p[s], s));
	set<int> st;
	b[s] = true;
	while (!que.empty()) {
		int x = que.top().second;
		int y = que.top().first;
		que.pop();
		for (int i = 0; i < vec[x].size(); i++) {
			if (y > p[vec[x][i]]) {
				st.insert(p[vec[x][i]]);
			}
			if (!b[vec[x][i]]) {
				que.push(make_pair(min(y, p[vec[x][i]]), vec[x][i]));
				b1[vec[x][i]] = max(b1[vec[x][i]],min(y, p[vec[x][i]]));
				b[vec[x][i]] = true;
			}
			else if (min(y, p[vec[x][i]]) > b1[vec[x][i]]) {
				que.push(make_pair(min(y, p[vec[x][i]]), vec[x][i]));
				b1[vec[x][i]] = max(b1[vec[x][i]], min(y, p[vec[x][i]]));
			}
			
		}
	}
	cout << st.size() << endl;
}