#include <bits/stdc++.h>
using namespace std;
namespace {
#define VEVE(i, a, b) for (ll i = a, __##i = b; i < __##i; ++i)
#define RARA(i, a, b) for (ll i = a, __##i = b; i > __##i; --i)
#define VERA(x, seq) for (auto &x : seq)
#define SIZE(x) ((ll)(x.size()))
#define ALL(x) x.begin(), x.end()
typedef long long ll;
typedef double dd;
const ll MAX_EDGES = 4004;
const ll INF = 1LL << 60;
vector<ll> to, pred, head, cost;
vector<vector<ll>> rev_adj;
ll dist[MAX_EDGES][MAX_EDGES];
vector<pair<ll, ll>> best_edges[MAX_EDGES][MAX_EDGES / 2]; // edge -> vertex -> (inc edge, dist)
// top 2 shortest distance from edge to vertex
void Min(ll& a, ll b) { a = min(a, b); }
void ComputeDist(ll n, ll m) {
priority_queue<pair<ll, ll>> pq; // (-dist, edge)
vector<ll> inc_count(n); // # of edges incident to vertex i processed
auto calc = [&](ll src_edge) {
fill(ALL(inc_count), 0);
dist[src_edge][src_edge] = 0;
pq.emplace(0, src_edge);
while (not pq.empty()) {
const auto cur_dist = -pq.top().first;
const auto edge = pq.top().second;
pq.pop();
if (cur_dist > dist[src_edge][edge])
continue;
if (++inc_count[to[edge]] > 2)
continue;
best_edges[src_edge][to[edge]].emplace_back(edge, cur_dist);
for (ll nx_edge = head[to[edge]]; ~nx_edge; nx_edge = pred[nx_edge]) {
// going back on same edge
if ((edge ^ nx_edge) == 1)
continue;
if (cur_dist + cost[nx_edge] < dist[src_edge][nx_edge]) {
dist[src_edge][nx_edge] = cur_dist + cost[nx_edge];
pq.emplace(-dist[src_edge][nx_edge], nx_edge);
}
}
}
};
memset(dist, 0x3F, sizeof(dist));
VEVE(e, 0, m) {
calc(e);
}
// PlnArr(dist, m, m);
}
void Solve(ll) {
ll n, m, t, l;
cin >> n >> m >> t >> l;
assert(t == 1);
head.resize(n, -1);
// rev_adj.resize(n);
VEVE(e, 0, m) {
ll a, b, c;
cin >> a >> b >> c;
--a, --b;
to.push_back(b);
cost.push_back(c);
pred.push_back(head[a]);
head[a] = SIZE(pred) - 1;
// rev_adj[b].push_back(head[a]);
to.push_back(a);
cost.push_back(c);
pred.push_back(head[b]);
head[b] = SIZE(pred) - 1;
// rev_adj[a].push_back(head[b]);
}
m *= 2;
ComputeDist(n, m);
vector<ll> supply(l);
VERA(s, supply) {
cin >> s;
--s;
}
vector<ll> dp_cur(m), dp_pred(m);
VEVE(_, 0, t) {
ll p, q;
cin >> p >> q;
--p, --q;
supply[p] = q;
fill(ALL(dp_pred), INF);
for (ll e = head[supply.front()]; ~e; e = pred[e]) {
dp_pred[e] = cost[e];
}
VEVE(i, 1, SIZE(supply)) {
fill(ALL(dp_cur), INF);
VEVE(pe, 0, m) {
if (dp_pred[pe] < INF) {
VERA(best, best_edges[pe][supply[i]]) {
Min(dp_cur[best.first], dp_pred[pe] + best.second);
}
}
}
// DEBUG(dp_cur);
swap(dp_pred, dp_cur);
}
ll res = *min_element(ALL(dp_pred));
if (res >= INF / 2)
res = -1;
cout << res << '\n';
}
}
void Init() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
}
}
int main() {
#ifdef AZN
freopen("input.txt", "r", stdin);
#endif
Init();
ll tests = 1;
VEVE(test, 1, tests + 1) Solve(test);
return 0;
}
