#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------

template<int um> class UF {
	public:
	vector<int> par,rank,cnt;
	UF() {par=rank=vector<int>(um,0); cnt=vector<int>(um,1); for(int i=0;i<um;i++) par[i]=i;}
	void reinit(int num=um) {int i; FOR(i,num) rank[i]=0,cnt[i]=1,par[i]=i;}
	int operator[](int x) {return (par[x]==x)?(x):(par[x] = operator[](par[x]));}
	int count(int x) { return cnt[operator[](x)];}
	int operator()(int x,int y) {
		if((x=operator[](x))==(y=operator[](y))) return x;
		cnt[y]=cnt[x]=cnt[x]+cnt[y];
		if(rank[x]>rank[y]) return par[x]=y;
		rank[x]+=rank[x]==rank[y]; return par[y]=x;
	}
};
UF<101010> uf;
int N,M,S,T;
int P[101010];
pair<int,int> X[101010];
vector<int> E[101010];
int vis[101010];

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>N>>M>>S>>T;
	S--;
	FOR(i,N) {
		cin>>P[i];
		X[i]={-P[i],i};
	}
	FOR(i,N) if(P[i]>=P[S]) vis[i]=1;
	sort(X,X+N);
	FOR(i,M) {
		cin>>x>>y;
		x--,y--;
		E[x].push_back(y);
		E[y].push_back(x);
		if(P[x]>=P[S]&&P[y]>=P[S]) uf(x,y);
	}
	int pre=P[S],ret=0;
	FOR(i,N) {
		j=X[i].second;
		if(vis[j]) continue;
		vis[j]=1;
		FORR(e,E[j]) if(vis[e]) {
			uf(e,j);
			if(uf[j]==uf[S]&&P[j]<pre) {
				pre=P[j];
				ret++;
			}
		}
	}
	cout<<ret<<endl;
	
		
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}