#include <bits/stdc++.h>

using namespace std;

typedef pair<int, int> P;
typedef pair<int, P> Pi;
typedef long long ll;
struct edge{
  int to; ll dist;
  edge(){}
  edge(int to, ll dist):to(to), dist(dist){}
};
const ll inf = 1LL << 55;

vector< vector<edge> > G(110);
ll minkal[1<<8][110];

int m, n, k, d;
ll cake[8];

ll dijkstra()
{
  fill(minkal[0], minkal[1<<8], inf);
  priority_queue<Pi, vector<Pi>, greater<Pi> > que;
  que.push(Pi(0, P(0, 0)));
  minkal[0][0] = 0;
  while(!que.empty()){
    Pi p = que.top(); que.pop();
    int vd = p.second.second, now = p.second.first; ll kal = p.first;
    if(minkal[vd][now] < kal) continue;    
    for(int i = 0; i < G[now].size(); i++){
      edge e = G[now][i];      
      if(0 < e.to && e.to <= m){
	if(!((vd >> (e.to - 1)) & 1)){
	  if(minkal[vd | (1 << (e.to-1))][e.to] > kal + e.dist*k - cake[e.to-1]){
	    que.push(Pi(kal + e.dist*k - cake[e.to-1], P(e.to, vd | (1<<(e.to-1)))));
	    minkal[vd | (1 << (e.to-1))][e.to] = kal + e.dist*k - cake[e.to-1];
	  }
	}
      } else if(minkal[vd][e.to] > kal + e.dist*k){
	que.push(Pi(kal + e.dist*k, P(e.to, vd)));
	minkal[vd][e.to] = kal + e.dist*k;
      }
    }
  }
  ll ret = inf;
  for(int i = 0; i < 1<<m; i++){
    ret = min(ret, minkal[i][n + m + 1]);
  }
  return ret;
}

int main()
{
  while(cin >> m >> n >> k >> d, m || n || k || d){
    G.clear(); G.resize(m + n + 2);
    memset(cake, 0, sizeof(cake));
    for(int i = 0; i < m; i++) cin >> cake[i];
    for(int i = 0; i < d; i++){
      string f_str, t_str; int from, to; ll dist;
      cin >> f_str >> t_str >> dist;
      if(f_str[0] == 'H') from = 0;
      if(f_str[0] == 'D') from = n + m + 1;
      if(f_str[0] == 'C') from = atoi(f_str.substr(1).c_str());
      if(f_str[0] == 'L') from = atoi(f_str.substr(1).c_str()) + m;
      if(t_str[0] == 'H') to = 0;
      if(t_str[0] == 'D') to = n + m + 1;
      if(t_str[0] == 'C') to = atoi(t_str.substr(1).c_str());
      if(t_str[0] == 'L') to = atoi(t_str.substr(1).c_str()) + m;
      G[from].push_back(edge(to, dist));
      G[to].push_back(edge(from, dist));
    }
    cout << dijkstra() << endl;
  }
  return 0;
}