#include<bits/stdc++.h>

using namespace std;
using ll = long long;
using pint = pair<int,int>;

#pragma region UnionFind
#define UNIONFIND
class UnionFind{
  private:
	vector<int> data;
  public:
	UnionFind(int n) : data(n,-1) {}
	int root(int i) { return data[i] < 0 ? i : data[i] = root(data[i]); }
	int size(int i) { return -data[root(i)]; }
	bool same(int x, int y) {return root(x) == root(y); }
	bool connected() {return size(0) == (int)data.size(); }

	bool unit(int i,int j){
		i = root(i);
		j = root(j);
		if(i != j){
			data[i] += data[j];
			data[j] = i;
		}
		return i != j;
	}
};
#pragma endregion
// #include"debug.hpp"

int main()
{
	int n, m, s, t; cin >> n >> m >> s >> t;
	s--,t--;
	vector<int> p(n);
	vector<vector<int>> hen(n);
	vector<tuple<int,int,int>> edge;
	for(auto &i : p) cin >> i;
	UnionFind uf(n);
	for(int i = 0; i < m; i++) {
		int u, v; cin >> u >> v;
		u--,v--;
		edge.emplace_back(u, v, p[v]);
		edge.emplace_back(v, u, p[u]);
	}
	sort(edge.begin(), edge.end(), [&](tuple<int,int,int>& x, tuple<int,int,int>& y){return get<2>(x) > get<2>(y);});
	int e = edge.size();
	// print(edge);


	int sum = 0;
	set<int> st;
	st.insert(s);
	int X = p[s];
	for(int i = 0; i < e; i++) {
		auto [from, to, cost] = edge[i];
		// if(uf.same(from, to)) continue;
		if(uf.same(from, s) == 1) {
			if(!st.count(to) && cost < X)sum++;
			st.insert(to);
		}
		uf.unit(from, to);
		X = min(cost, X);
	}
	cout << sum << endl;
}