#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); }
};

int main() {
  int n, q, c; cin >> n >> q >> c;
  vector<vector<Edge<int>>> 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];
  vector<ll> dp(n, LINF);
  dp[x[0]] = 0;
  FOR(i, 1, q) {
    vector<int> path;
    vector<ll> dist;
    ll sum = 0;
    auto dfs = [&](auto &&dfs, int par, int ver) -> bool {
      if (ver == x[i]) return true;
      for (const Edge<int> e : graph[ver]) {
        if (e.dst != par) {
          path.emplace_back(e.dst);
          dist.emplace_back(e.cost);
          sum += e.cost;
          if (dfs(dfs, ver, e.dst)) return true;
          sum -= e.cost;
          dist.pop_back();
          path.pop_back();
        }
      }
      return false;
    };
    dfs(dfs, -1, x[i - 1]);
    int m = path.size();
    vector<ll> cum(m, 0);
    for (int i = m - 2; i >= 0; --i) cum[i] = cum[i + 1] + dist[i + 1];
    vector<ll> jump(m, LINF);
    REP(i, m) jump[i] = dp[path[i]] + c + cum[i];
    ll mn = LINF;
    REP(i, n) {
      dp[i] += sum;
      chmin(mn, dp[i]);
    }
    REP(i, m) {
      chmin(mn, jump[i]);
      chmin(dp[path[i]], mn);
    }
  }
  cout << *min_element(ALL(dp)) << '\n';
  return 0;
}