#include<iostream>
#include<string>
#include<iomanip>
#include<cmath>
#include<vector>
#include<algorithm>
#include<utility>

using namespace std;

#define int long long
#define endl "\n"

constexpr long long INF = (long long)1e18;
constexpr long long MOD = 1'000'000'007; 

struct fast_io {
	fast_io(){
		std::cin.tie(nullptr);
		std::ios::sync_with_stdio(false);
	};
} fio;


class union_find
{
	int  _setnum;
	vector<int> par, nume;
public:
	union_find(){
	}
	
	union_find(int x){
		par.resize(x);
		nume.resize(x);
		init();
	}
	
	~union_find(){
		//
		
	}
	
	void clear(){
		_setnum = 0;
		par.clear();
		nume.clear();
	}
	
	void init(){
		_setnum = par.size();
		for(int i = 0; i < par.size(); i++){
			par[i] = i;
			nume[i] = 1;
		}
	}
	
	void resize(int x){
		
		par.resize(x);
		nume.resize(x);
		init();
	}

	int find(int x){
		return par[x] == x ? x : par[x] = find(par[x]);
	}

	void unite(int x, int y){
		x = find(x);
		y = find(y);
	
		if(x == y)return;
		
		_setnum--;
		
		if(nume[x] > nume[y]) std::swap(x,y);
		
		par[x] = y;
		nume[y] += nume[x];
	}
	
	bool same(int x, int y){
		return find(x) == find(y);
	}
	
	int numel(int x){
		return nume[find(x)];
	}
	
	int size(){
		return par.size();
	}
	
	int setnum(){
		return _setnum;
	}
};

signed main(){
	cout<<fixed<<setprecision(10);
	
	int N, M, S, T;
    int X, Y = 0;
	vector<int> p;
	vector<pair<int,int>> num;
    vector<vector<int>> G;
    union_find uf;
    
    cin>>N>>M>>S>>T;
    
    S--, T--;
    
    
	
    p.resize(N);
    uf.resize(N);
    G.resize(N);
    
    for(int i = 0; i < N; i++){
        cin>>p[i];
        num.push_back({p[i], i});
    }
    
    X = p[S];
    
    for(int i = 0; i < M; i++){
        int a, b;
        
        cin>>a>>b;
        
        a--, b--;
        
        G[a].push_back(b);
        G[b].push_back(a);
    }
    
    sort(num.begin(), num.end(), greater<pair<int,int>>());
    
    for(int i = 0; i < num.size(); i++){
        for(int y : G[num[i].second]){
            if(p[y] < num[i].first) continue;
            uf.unite(num[i].second, y);
            
            if(uf.same(num[i].second, S) && num[i].first < X) {
                Y++;
                X = num[i].first;
            }                
        }
    }
    
    cout<<Y<<endl;
    
	return 0;
}