#include <bits/stdc++.h>
using namespace std;
using LL=long long;
using ULL=unsigned long long;
#define rep(i,n) for(int i=0; i<(n); i++)

int N,M,S,T;
int P[100000];
vector<int> E[100000];
bool F[100000];

int main(){
  scanf("%d%d%d%d",&N,&M,&S,&T); S--; T--;
  rep(i,N) scanf("%d",&P[i]);
  rep(i,M){
    int u,v; scanf("%d%d",&u,&v); u--; v--;
    E[u].push_back(v);
    E[v].push_back(u);
  }

  rep(i,N) F[i]=false;
  priority_queue<pair<int,int>> Q;
  F[S]=true; Q.push({P[S],S});
  int X=P[S];
  int Y=0;
  while(Q.size()){
    int p=Q.top().second; Q.pop();
    if(X>P[p]){ X=P[p]; Y++; }
    for(int e:E[p]){
      if(F[e]) continue; F[e]=true;
      Q.push({P[e],e});
    }
  }

  printf("%d\n",Y);
  return 0;
}