#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < n; i++)
#define rep2(i, x, n) for(int i = x; i <= n; i++)
#define rep3(i, x, n) for(int i = x; i >= n; i--)
#define each(e, v) for(auto &e: v)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) (int)x.size()
using ll = long long;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
const int MOD = 1000000007;
//const int MOD = 998244353;
const int inf = (1<<30)-1;
const ll INF = (1LL<<60)-1;
template<typename T> bool chmax(T &x, const T &y) {return (x < y)? (x = y, true) : false;};
template<typename T> bool chmin(T &x, const T &y) {return (x > y)? (x = y, true) : false;};

struct io_setup{
    io_setup(){
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        cout << fixed << setprecision(15);
    }
} io_setup;

vector<vector<ll>> D;

template<typename T>
struct Weighted_Graph{
    struct edge{
        int to; T cost;
        edge(int to, T cost) : to(to), cost(cost) {}
    };

    vector<vector<edge>> es;
    vector<T> d;
    vector<int> pre_v;
    vector<int> keep;
    const T INF_T;
    const int n;

    Weighted_Graph(int n) : INF_T(numeric_limits<T>::max()), n(n){
        es.resize(n), d.resize(n), pre_v.resize(n);
    }

    void add_edge(int from, int to, T cost, bool directed = false){
        es[from].eb(to, cost);
        if(!directed) es[to].eb(from, cost);
    }

    void dfs(int s, int now, int pre){
        each(e, es[now]){
            if(e.to == pre) continue;
            D[s][e.to] = D[s][now]+e.cost;
            dfs(s, e.to, now);
        }
    }

    void dijkstra(vector<T> v){
        using P = pair<T, int>;
        priority_queue<P, vector<P>, greater<P> > que;
        rep(i, n){
            que.emplace(d[i] = v[i], i);
        }
        while(!que.empty()){
            auto [p, i] = que.top(); que.pop();
            if(p > d[i]) continue;
            each(e, es[i]){
                if(chmin(d[e.to], d[i]+e.cost)){
                    pre_v[e.to] = i, que.emplace(d[e.to], e.to);
                }
            }
        }
    }

    vector<int> shortest_path(int s, int t){
        keep.clear();
        if(dijkstra(s, t) == INF_T) return keep;
        for(int now = t; now != s; now = pre_v[now]) keep.pb(now);
        keep.pb(s), reverse(all(keep));
        return keep;
    }
};

int main(){
    int N, Q; ll C;
    cin >> N >> Q >> C;
    Weighted_Graph<ll> G(N);
    rep(i, N-1){
        int u, v; ll c;
        cin >> u >> v >> c; u--, v--;
        G.add_edge(u, v, c);
    }
    vector<int> x(Q);
    rep(i, Q) {cin >> x[i]; x[i]--;}

    D.assign(N, vector<ll>(N, INF));
    rep(i, N){
        D[i][i] = 0;
        G.dfs(i, i, -1);
    }
    
    vector<vector<ll>> dp(Q, vector<ll>(N, INF));
    dp[0][x[0]] = 0;
    rep(i, Q-1){
        vector<ll> tmp(N, INF);
        rep(j, N){
            chmin(tmp[j], C+dp[i][j]), chmin(tmp[x[i]], dp[i][j]);
        }
        G.dijkstra(tmp);
        rep(j, N){
            chmin(dp[i+1][j], dp[i][j]+D[x[i]][x[i+1]]);
            chmin(dp[i+1][j], G.d[j]+D[j][x[i+1]]);
        }
    }

    ll ans = INF;
    rep(i, N) chmin(ans, dp[Q-1][i]);
    cout << ans << '\n';
}