#include <bits/stdc++.h>
using namespace std;

using VI = vector<int>;
using VVI = vector<VI>;
using PII = pair<int, int>;
using LL = long long;
using VL = vector<LL>;
using VVL = vector<VL>;
using PLL = pair<LL, LL>;
using VS = vector<string>;

#define ALL(a)  begin((a)),end((a))
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define EB emplace_back
#define MP make_pair
#define SZ(a) int((a).size())
#define SORT(c) sort(ALL((c)))
#define RSORT(c) sort(RALL((c)))
#define UNIQ(c) (c).erase(unique(ALL((c))), end((c)))

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)

#define FF first
#define SS second
template<class S, class T>
istream& operator>>(istream& is, pair<S,T>& p){
  return is >> p.FF >> p.SS;
}
template<class S, class T>
ostream& operator<<(ostream& os, const pair<S,T>& p){
  return os << p.FF << " " << p.SS;
}
template<class T>
void maxi(T& x, T y){
  if(x < y) x = y;
}
template<class T>
void mini(T& x, T y){
  if(x > y) x = y;
}


const double EPS = 1e-10;
const double PI  = acos(-1.0);
const LL MOD = 1e9+7;

int main(){
  cin.tie(0);
  ios_base::sync_with_stdio(false);

  int N, M, H, K;
  while(cin>>N>>M>>H>>K,N){
	VI xs(N);
	REP(i,N) cin >> xs[i];
	VVI es(H);
	REP(i,M){
	  int x, y;
	  cin >> x >> y;
	  --x, --y;
	  es[y].EB(x);
	}

	VI f(N), fi(N), g(N), gi(N);
	iota(ALL(f), 0);
	iota(ALL(fi), 0);
	iota(ALL(g), 0);
	iota(ALL(gi), 0);
	REP(y,H){
	  for(int x: es[y]){
		swap(g[gi[x]], g[gi[x+1]]);
		swap(gi[x], gi[x+1]);
	  }
	}

	int ans = 0;
	REP(i,K) ans += xs[g[i]];
	REP(y,H){
	  for(int x: es[y]){
		swap(f[fi[x]], f[fi[x+1]]);
		swap(fi[x], fi[x+1]);
		swap(g[x], g[x+1]);
	  }
	  for(int x: es[y]){
		int sum = 0;
		swap(fi[x], fi[x+1]);
		swap(f[fi[x]], f[fi[x+1]]);
		REP(i,K){
		  sum += xs[g[f[i]]];
		}
		mini(ans, sum);
		swap(f[fi[x]], f[fi[x+1]]);
		swap(fi[x], fi[x+1]);
	  }
	}
	cout << ans << endl;
  }

  return 0;
}