#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 1000000007;
// constexpr int MOD = 998244353;
constexpr int dy[] = {1, 0, -1, 0}, dx[] = {0, -1, 0, 1};
constexpr int dy8[] = {1, 1, 0, -1, -1, -1, 0, 1}, dx8[] = {0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U> inline bool chmax(T &a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U> inline bool chmin(T &a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

template <typename CostType>
struct Edge {
  int src, dst; CostType cost;
  Edge(int src, int dst, CostType cost = 0) : src(src), dst(dst), cost(cost) {}
  inline bool operator<(const Edge &x) const {
    return cost != x.cost ? cost < x.cost : dst != x.dst ? dst < x.dst : src < x.src;
  }
  inline bool operator<=(const Edge &x) const { return !(x < *this); }
  inline bool operator>(const Edge &x) const { return x < *this; }
  inline bool operator>=(const Edge &x) const { return !(*this < x); }
};

template <typename CostType>
struct HLD {
  std::vector<int> parent, subtree, id, inv, head;
  std::vector<CostType> cost;

  HLD(const std::vector<std::vector<Edge<CostType>>> &graph, int root = 0) : graph(graph) {
    int n = graph.size();
    parent.assign(n, -1);
    subtree.assign(n, 1);
    id.resize(n);
    inv.resize(n);
    head.resize(n);
    dfs1(root);
    head[root] = root;
    int now_id = 0;
    dfs2(root, now_id);
  }

  template <typename Fn>
  void v_update(int u, int v, Fn f) const {
    while (true) {
      if (id[u] > id[v]) std::swap(u, v);
      f(std::max(id[head[v]], id[u]), id[v] + 1);
      if (head[u] == head[v]) return;
      v = parent[head[v]];
    }
  }

  template <typename T, typename F, typename G>
  T v_query(int u, int v, F f, G g, const T UNITY) const {
    T left = UNITY, right = UNITY;
    while (true) {
      if (id[u] > id[v]) {
        std::swap(u, v);
        std::swap(left, right);
      }
      left = g(left, f(std::max(id[head[v]], id[u]), id[v] + 1));
      if (head[u] == head[v]) break;
      v = parent[head[v]];
    }
    return g(left, right);
  }

  template <typename Fn>
  void subtree_v_update(int ver, Fn f) const { f(id[ver], id[ver] + subtree[ver]); }

  template <typename T, typename Fn>
  T subtree_v_query(int ver, Fn f) const { return f(id[ver], id[ver] + subtree[ver]); }

  template <typename Fn>
  void e_update(int u, int v, Fn f) const {
    while (true) {
      if (id[u] > id[v]) std::swap(u, v);
      if (head[u] == head[v]) {
        f(id[u], id[v]);
        break;
      } else {
        f(id[head[v]] - 1, id[v]);
        v = parent[head[v]];
      }
    }
  }

  template <typename T, typename F, typename G>
  T e_query(int u, int v, F f, G g, const T UNITY) const {
    T left = UNITY, right = UNITY;
    while (true) {
      if (id[u] > id[v]) {
        std::swap(u, v);
        std::swap(left, right);
      }
      if (head[u] == head[v]) {
        left = g(left, f(id[u], id[v]));
        break;
      } else {
        left = g(left, f(id[head[v]] - 1, id[v]));
        v = parent[head[v]];
      }
    }
    return g(left, right);
  }

  template <typename Fn>
  void subtree_e_update(int ver, Fn f) const { f(id[ver], id[ver] + subtree[ver] - 1); }

  template <typename T, typename Fn>
  T subtree_e_query(int ver, Fn f) const { return f(id[ver], id[ver] + subtree[ver] - 1); }

  int lca(int u, int v) const {
    while (true) {
      if (id[u] > id[v]) std::swap(u, v);
      if (head[u] == head[v]) return u;
      v = parent[head[v]];
    }
  }

private:
  std::vector<std::vector<Edge<CostType>>> graph;

  void dfs1(int ver) {
    for (Edge<CostType> &e : graph[ver]) {
      if (e.dst != parent[ver]) {
        parent[e.dst] = ver;
        dfs1(e.dst);
        subtree[ver] += subtree[e.dst];
        if (subtree[e.dst] > subtree[graph[ver].front().dst]) std::swap(e, graph[ver].front());
      }
    }
  }

  void dfs2(int ver, int &now_id) {
    id[ver] = now_id++;
    inv[id[ver]] = ver;
    for (const Edge<CostType> &e : graph[ver]) {
      if (e.dst != parent[ver]) {
        head[e.dst] = (e.dst == graph[ver].front().dst ? head[ver] : e.dst);
        cost.emplace_back(e.cost);
        dfs2(e.dst, now_id);
      }
    }
  }
};

template <typename CostType>
struct LCADoubling {
  std::vector<int> depth;
  std::vector<CostType> dist;

  LCADoubling(const std::vector<std::vector<Edge<CostType>>> &graph) : graph(graph) {
    n = graph.size();
    depth.resize(n);
    dist.resize(n);
    while ((1 << table_h) <= n) ++table_h;
    parent.resize(table_h, std::vector<int>(n));
  }

  void build(int root = 0) {
    is_built = true;
    dfs(-1, root, 0, 0);
    for (int i = 0; i + 1 < table_h; ++i) for (int ver = 0; ver < n; ++ver) {
      parent[i + 1][ver] = parent[i][ver] == -1 ? -1 : parent[i][parent[i][ver]];
    }
  }

  int query(int u, int v) const {
    assert(is_built);
    if (depth[u] > depth[v]) std::swap(u, v);
    for (int i = 0; i < table_h; ++i) {
      if ((depth[v] - depth[u]) >> i & 1) v = parent[i][v];
    }
    if (u == v) return u;
    for (int i = table_h - 1; i >= 0; --i) {
      if (parent[i][u] != parent[i][v]) {
        u = parent[i][u];
        v = parent[i][v];
      }
    }
    return parent[0][u];
  }

  CostType distance(int u, int v) const {
    assert(is_built);
    return dist[u] + dist[v] - dist[query(u, v)] * 2;
  }

private:
  bool is_built = false;
  int n, table_h = 1;
  std::vector<std::vector<Edge<CostType>>> graph;
  std::vector<std::vector<int>> parent;

  void dfs(int par, int ver, int now_depth, CostType now_dist) {
    depth[ver] = now_depth;
    dist[ver] = now_dist;
    parent[0][ver] = par;
    for (const Edge<CostType> &e : graph[ver]) {
      if (e.dst != par) dfs(ver, e.dst, now_depth + 1, now_dist + e.cost);
    }
  }
};

int main() {
  int n, q, c; cin >> n >> q >> c;
  vector<vector<Edge<ll>>> graph(n);
  REP(_, n - 1) {
    int u, v, l; cin >> u >> v >> l; --u; --v;
    graph[u].emplace_back(u, v, l);
    graph[v].emplace_back(v, u, l);
  }
  vector<int> x(q); REP(i, q) cin >> x[i], --x[i];
  HLD hld(graph);
  LCADoubling lca(graph);
  lca.build();
  vector<ll> dp(n, LINF);
  dp[x[0]] = 0;
  FOR(i, 1, q) {
    vector<vector<ll>> ins(n + 1), era(n + 1);
    REP(v, n) {
      ll t = dp[v] + c + lca.distance(v, x[i]);
      hld.v_update(v, x[i], [&](int a, int b) {
        ins[a].emplace_back(t);
        era[b].emplace_back(t);
      });
    }
    ll thr = *min_element(ALL(dp)) + lca.distance(x[i - 1], x[i]);
    hld.v_update(x[i - 1], x[i], [&](int a, int b) {
      ins[a].emplace_back(thr);
      era[b].emplace_back(thr);
    });
    vector<ll> nx(n, LINF);
    map<ll, int> mp;
    REP(j, n) {
      for (ll e : ins[j]) ++mp[e];
      for (ll e : era[j]) {
        --mp[e];
        if (mp[e] == 0) mp.erase(e);
      }
      if (!mp.empty()) nx[j] = mp.begin()->first;
    }
    REP(j, n) {
      dp[j] += lca.distance(x[i - 1], x[i]);
      chmin(dp[j], nx[hld.id[j]]);
    }
  }
  cout << *min_element(ALL(dp)) << '\n';
  return 0;
}