/**
 * @brief 並列二分探索
 * @author えびちゃん
 */

#ifndef H_parallel_binary_search
#define H_parallel_binary_search

#include <cstddef>
#include <vector>

template <typename StatefulPredicate, typename RandomIt>
std::vector<size_t> parallel_binary_search(
    StatefulPredicate spred, RandomIt first, RandomIt last
) {
  // result[i] = j if spred(first[i]) returns true state j-1 (and before
  // that) and returns false state j (and after that).
  size_t size = spred.size();
  std::vector<size_t> lb(std::distance(first, last), 0);
  std::vector<size_t> ub(lb.size(), size+1);
  bool determined = false;
  while (!determined) {
    determined = true;
    std::vector<std::vector<RandomIt>> ev(size+1);
    auto it = first;
    for (size_t i = 0; i < lb.size(); ++i) {
      auto cur = it++;
      if (!(ub[i] - lb[i] > 1)) continue;
      size_t mid = (lb[i] + ub[i]) >> 1;
      ev[mid].push_back(cur);
      determined = false;
    }
    auto sp = spred;
    for (size_t i = 0; i <= size; ++i) {
      for (auto const& e: ev[i]) {
        (sp(*e)? lb[e-first]: ub[e-first]) = i;
      }
      if (i < size) sp.next();
    }
  }
  return ub;
}

#endif  /* !defined(H_parallel_binary_search) */

/**
 * @brief 素集合データ構造
 * @author えびちゃん
 */

#ifndef H_union_find
#define H_union_find

#include <cstddef>
#include <cstdint>
#include <utility>
#include <vector>

class disjoint_set {
public:
  using size_type = size_t;

private:
  mutable std::vector<intmax_t> M_c;

public:
  disjoint_set() = default;
  disjoint_set(disjoint_set const&) = default;
  disjoint_set(disjoint_set&&) = default;

  explicit disjoint_set(size_type n): M_c(n, -1) {}

  disjoint_set& operator =(disjoint_set const&) = default;
  disjoint_set& operator =(disjoint_set&&) = default;

  void reset() { M_c.assign(M_c.size(), -1); }

  size_type representative(size_type v) const {
    if (M_c[v] < 0) return v;
    return (M_c[v] = representative(M_c[v]));
  }

  bool unite(size_type u, size_type v) {
    u = representative(u);
    v = representative(v);
    if (u == v) return false;
    if (-M_c[u] > -M_c[v]) std::swap(u, v);
    M_c[v] += M_c[u];
    M_c[u] = v;
    return true;
  }

  bool equivalent(size_type u, size_type v) const {
    return (representative(u) == representative(v));
  }

  size_type size() const noexcept { return M_c.size(); }
  size_type count(size_type v) const {
    return -M_c[representative(v)];
  }
};

#endif  /* !defined(H_union_find) */

/**
 * @brief 重みつきグラフの隣接リスト
 * @author えびちゃん
 */

#ifndef H_adjacency_list
#define H_adjacency_list

#include <cstddef>
#include <algorithm>
#include <type_traits>
#include <vector>

template <typename WeightType>
class weighted_edge {
public:
  using size_type = size_t;
  using weight_type = WeightType;

protected:
  size_type M_src, M_dst;
  weight_type M_weight;

public:
  weighted_edge() = default;
  weighted_edge(weighted_edge const&) = default;
  weighted_edge(weighted_edge&&) = default;

  weighted_edge(size_type s, size_type d, weight_type w):
    M_src(s), M_dst(d), M_weight(w)
  {}

  weighted_edge& operator =(weighted_edge const&) = default;
  weighted_edge& operator =(weighted_edge&&) = default;

  bool operator <(weighted_edge const& other) const {
    if (M_weight < other.M_weight) return true;
    if (other.M_weight < M_weight) return false;
    if (M_src != other.M_src) return M_src < other.M_src;
    return M_dst < other.M_dst;
  }

  size_type source() const { return M_src; }
  size_type target() const { return M_dst; }
  weight_type weight() const { return M_weight; }
};

struct directed_tag {};
struct undirected_tag {};

template <typename Edge, typename Directedness>
class adjacency_list {
public:
  using size_type = size_t;
  using edge_type = Edge;
  using weight_type = typename Edge::weight_type;

private:
  std::vector<std::vector<edge_type>> M_g;

public:
  adjacency_list() = default;
  adjacency_list(adjacency_list const&) = default;
  adjacency_list(adjacency_list&&) = default;
  explicit adjacency_list(size_type n): M_g(n) {}

  template <typename... Args>
  void emplace(size_type src, size_type dst, Args... args) {
    M_g[src].emplace_back(src, dst, args...);
    if (std::is_same<Directedness, undirected_tag>::value)
      M_g[dst].emplace_back(dst, src, args...);
  }

  void sort_by_index() {
    auto cmp = [](auto const& e1, auto const& e2) {
      return e1.target() < e2.target();
    };
    for (auto v: M_g) std::sort(v.begin(), v.end(), cmp);
  }

  size_type size() const { return M_g.size(); }
  auto const& operator [](size_type i) const { return M_g[i]; }
};

#endif  /* !defined(H_adjacency_list) */

/**
 * @brief 型依存の定数
 * @author えびちゃん
 */

#include <limits>

#ifndef H_limits
#define H_limits

template <typename Tp>
class limits: public std::numeric_limits<Tp> {};

#endif  /* !defined(H_limits) */

#include <cstdio>
#include <cstdint>
#include <algorithm>
#include <functional>
#include <map>
#include <queue>
#include <tuple>
#include <vector>

class spred {
  disjoint_set M_ds;
  std::vector<std::vector<std::pair<size_t, size_t>>> M_es;
  size_t M_st;

public:
  spred() = default;
  spred(size_t n, std::vector<std::vector<std::pair<size_t, size_t>>> const& es):
    M_ds(n), M_es(es), M_st(es.size()) {}

  void next() {
    for (auto const& e: M_es[--M_st]) M_ds.unite(e.first, e.second);
  }

  bool operator ()(std::pair<size_t, size_t> const& e) {
    return !M_ds.equivalent(e.first, e.second);
  }

  size_t size() const { return M_es.size(); }
};

template <typename Tp>
using greater_priority_queue = std::priority_queue<Tp, std::vector<Tp>, std::greater<>>;

int main() {
  size_t n, m, k, q;
  scanf("%zu %zu %zu %zu", &n, &m, &k, &q);

  adjacency_list<weighted_edge<int>, undirected_tag> g(n);
  for (size_t i = 0; i < m; ++i) {
    size_t u, v;
    int w;
    scanf("%zu %zu %d", &u, &v, &w);
    --u, --v;
    g.emplace(u, v, w);
  }

  std::vector<size_t> f(k);
  for (auto& fi: f) scanf("%zu", &fi), --fi;

  std::vector<int> dist(n, limits<int>::max());
  greater_priority_queue<std::pair<int, size_t>> pq;
  for (auto fi: f) {
    dist[fi] = 0;
    pq.emplace(0, fi);
  }

  while (!pq.empty()) {
    int w;
    size_t v;
    std::tie(w, v) = pq.top();
    pq.pop();
    if (w > dist[v]) continue;
    for (auto const& e: g[v]) {
      size_t nv = e.target();
      int nw = dist[v] + e.weight();
      if (dist[nv] > nw) {
        dist[nv] = nw;
        pq.emplace(nw, nv);
      }
    }
  }

  std::map<int, size_t> enc;
  std::vector<int> dec;
  for (auto d: dist) enc[d];
  {
    size_t i = 0;
    for (auto& p: enc) {
      p.second = i++;
      dec.push_back(p.first);
    }
  }

  std::vector<std::vector<std::pair<size_t, size_t>>> es(dec.size());
  for (size_t i = 0; i < n; ++i) {
    for (auto const& e: g[i]) {
      size_t u = e.source();
      size_t v = e.target();
      if (dist[u] + e.weight() <= dist[v]) {
        es[enc.at(dist[u])].emplace_back(u, v);
      }
      if (dist[u] <= dist[v]) {
        es[enc.at(dist[u])].emplace_back(u, v);
      }
    }
  }

  std::vector<std::pair<size_t, size_t>> st(q);
  for (auto& p: st) scanf("%zu %zu", &p.first, &p.second), --p.first, --p.second;

  auto res = parallel_binary_search(spred(n, es), st.begin(), st.end());
  for (auto ri: res) printf("%d\n", dec[es.size()-ri]);
}


Measured memory_bytes: 49880