#include<bits/stdc++.h>
#include<atcoder/all>
using namespace std;
using namespace atcoder;
typedef long long int ll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
typedef vector<vvvl> vvvvl;
typedef vector<bool> vb;
typedef vector<vb> vvb;
typedef vector<vvb> vvvb;
typedef vector<vvvb> vvvvb;
typedef pair<ll,ll> pl;
typedef pair<ll,pl> ppl;
typedef pair<ll,ppl> pppl;
typedef pair<ll,pppl> pppppl;
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define rrep(i,a,b) for(int i=(b)-1;i>=(a);i--)
#define all(a) begin(a),end(a)
#define sz(a) (int)(a).size()
#define F first
#define S second
#define bs(A,x) binary_search(all(A),x)
#define lb(A,x) (ll)(lower_bound(all(A),x)-A.begin())
#define ub(A,x) (ll)(upper_bound(all(A),x)-A.begin())
#define cou(A,x) (ll)(upper_bound(all(A),x)-lower_bound(all(A),x))
template<typename T>using min_priority_queue=priority_queue<T,vector<T>,greater<T>>;
template<class T>bool chmax(T&a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T>bool chmin(T&a,T b){if(b<a){a=b;return 1;}return 0;}
//*
using mint=modint998244353;
const ll mod=998244353;
//*/
/*
using mint=modint1000000007;
const ll mod=1000000007;
//*/
//using mint=modint;
//*
typedef vector<mint> vm;
typedef vector<vm> vvm;
typedef vector<vvm> vvvm;
typedef vector<vvvm> vvvvm;
ostream&operator<<(ostream&os,mint a){os<<a.val();return os;}
istream&operator>>(istream&is,mint&a){int x;is>>x;a=mint(x);return is;}
//*/
template<typename T1,typename T2>ostream&operator<<(ostream&os,pair<T1,T2>p){os<<p.F<<" "<<p.S;return os;}
template<typename T1,typename T2>istream&operator>>(istream&is,pair<T1,T2>&p){is>>p.F>>p.S;return is;}
template<typename T>ostream&operator<<(ostream&os,vector<T>v){rep(i,0,sz(v))os<<v[i]<<(i+1!=sz(v)?" ":"");return os;}
template<typename T>istream&operator>>(istream&is,vector<T>&v){for(T&in:v)is>>in;return is;}
int main(){
  cin.tie(0)->sync_with_stdio(0);
  cin.exceptions(cin.failbit);
  ll N,M,X,K;cin>>N>>M>>X>>K;
  vl A(N);cin>>A;
  vector<vector<pl>>E(N);
  vl U(M),V(M);
  rep(i,0,M){
  	ll u,v;cin>>u>>v;u--;v--;
  	if(abs(A[u]-A[v])>X)continue;
  	E[u].emplace_back(v,i);
  	E[v].emplace_back(u,i);
  	U[i]=u;V[i]=v;
  }
  if(K==2){
  	dsu D(N);
  	rep(i,0,N)for(auto[j,_]:E[i])D.merge(i,j);
  	auto gr=D.groups();
  	ll ans=-N;
  	for(auto g:gr)ans+=sz(g)*1ll*sz(g);
  	cout<<ans<<endl;
  	return 0;
  }
  dsu D(M);
  rep(i,0,N){
  	vector<pl>Q;
  	for(auto[j,_]:E[i])Q.emplace_back(A[j],_);
  	sort(all(Q));
  	rep(j,0,sz(Q)-1)if(max({A[i],Q[j].F,Q[j+1].F})-min({A[i],Q[j].F,Q[j+1].F})<=X)D.merge(Q[j].S,Q[j+1].S);
  }
  ll ans=-N;
  auto gr=D.groups();
  vector<bitset<200000>>B;
  vvl F(N);
  vl S;
  for(auto g:gr){
  	if(sz(g)==1&&U[g[0]]==V[g[0]])continue;
	B.emplace_back(0);
	for(auto v:g){
	  	B.back()[U[v]]=B.back()[V[v]]=1;
	  	F[U[v]].emplace_back(sz(S));
	  	F[V[v]].emplace_back(sz(S));
	}
	S.emplace_back(B.back().count());
  }
  rep(v,0,N){
  	sort(all(F[v]));
  	F[v].erase(unique(all(F[v])),F[v].end());
  	assert(sz(F[v])<=2);
  	if(sz(F[v])==0)ans++;
  	else if(sz(F[v])==1)ans+=S[F[v][0]];
  	else ans+=S[F[v][0]]+S[F[v][1]]-(B[F[v][0]]&B[F[v][1]]).count();
  }
  cout<<ans<<endl;
  return 0;
}