#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

using Int = long long;

template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
template <class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cerr << *i << " "; cerr << endl; }
template <class T> bool chmin(T &t, const T &f) { if (t > f) { t = f; return true; } return false; }
template <class T> bool chmax(T &t, const T &f) { if (t < f) { t = f; return true; } return false; }


constexpr Int INF = 1'000'000'000'000'000'000LL;
constexpr int MAX = 3010;

int N, Q;
Int C;
int A[MAX], B[MAX];
Int L[MAX];
int X[MAX];

vector<int> G[MAX];
void dfs(Int *dist, int u, int p, Int d) {
  dist[u] = d;
  for (const int i : G[u]) {
    const int v = A[i] ^ B[i] ^ u;
    if (v != p) {
      dfs(dist, v, u, d + L[i]);
    }
  }
}

void shortest(Int *ds) {
  using Node = pair<Int, int>;
  priority_queue<Node, vector<Node>, greater<Node>> que;
  for (int u = 0; u < N; ++u) {
    que.emplace(ds[u], u);
  }
  for (; !que.empty(); ) {
    const Int c = que.top().first;
    const int u = que.top().second;
    que.pop();
    if (ds[u] == c) {
      for (const int i : G[u]) {
        const int v = A[i] ^ B[i] ^ u;
        const Int cc = c + L[i];
        if (chmin(ds[v], cc)) {
          que.emplace(cc, v);
        }
      }
    }
  }
}

Int dist[MAX][MAX];
Int dp[MAX][MAX];
Int sub[MAX];

int main() {
  for (; ~scanf("%d%d%lld", &N, &Q, &C); ) {
    for (int i = 0; i < N - 1; ++i) {
      scanf("%d%d%lld", &A[i], &B[i], &L[i]);
      --A[i];
      --B[i];
    }
    for (int q = 0; q < Q; ++q) {
      scanf("%d", &X[q]);
      --X[q];
    }
    
    fill(G, G + N, vector<int>{});
    for (int i = 0; i < N - 1; ++i) {
      G[A[i]].push_back(i);
      G[B[i]].push_back(i);
    }
    
    for (int u = 0; u < N; ++u) {
      dfs(dist[u], u, -1, 0);
    }
    
    for (int q = 0; q < Q; ++q) {
      fill(dp[q], dp[q] + N, INF);
    }
    dp[0][X[0]] = 0;
    for (int q = 0; q < Q - 1; ++q) {
      for (int u = 0; u < N; ++u) {
        chmin(dp[q + 1][u], dp[q][u] + dist[X[q]][X[q + 1]]);
      }
      Int mn = INF;
      for (int u = 0; u < N; ++u) {
        sub[u] = dp[q][u] + C;
        chmin(mn, dp[q][u]);
      }
      chmin(sub[X[q]], mn);
      shortest(sub);
      for (int u = 0; u < N; ++u) {
        chmin(dp[q + 1][u], sub[u] + dist[u][X[q + 1]]);
      }
// pv(dp[q+1],dp[q+1]+N);
    }
    const Int ans = *min_element(dp[Q - 1], dp[Q - 1] + N);
    printf("%lld\n", ans);
  }
  return 0;
}