//*
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
//*/
 
#include <bits/stdc++.h>
 
// #include <atcoder/all>
 
using namespace std;
// using namespace atcoder;
 
#define DEBUG(x) cerr<<#x<<": "<<x<<endl;
#define DEBUG_VEC(v) cerr<<#v<<":";for(int i=0;i<v.size();i++) cerr<<" "<<v[i]; cerr<<endl;
#define DEBUG_MAT(v) cerr<<#v<<endl;for(int i=0;i<v.size();i++){for(int j=0;j<v[i].size();j++) {cerr<<v[i][j]<<" ";}cerr<<endl;}
typedef long long ll;
// #define int ll
 
#define vi vector<int>
#define vl vector<ll>
#define vii vector< vector<int> >
#define vll vector< vector<ll> >
#define vs vector<string>
#define pii pair<int,int>
#define pis pair<int,string>
#define psi pair<string,int>
#define pll pair<ll,ll>
template<class S, class T> pair<S, T> operator+(const pair<S, T> &s, const pair<S, T> &t) { return pair<S, T>(s.first + t.first, s.second + t.second); }
template<class S, class T> pair<S, T> operator-(const pair<S, T> &s, const pair<S, T> &t) { return pair<S, T>(s.first - t.first, s.second - t.second); }
template<class S, class T> ostream& operator<<(ostream& os, pair<S, T> p) { os << "(" << p.first << ", " << p.second << ")"; return os; }
#define X first
#define Y second
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define rep1(i,n) for(int i=1;i<=(int)(n);i++)
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;i--)
#define rrep1(i,n) for(int i=(int)(n);i>0;i--)
#define REP(i,a,b) for(int i=a;i<b;i++)
#define in(x, a, b) (a <= x && x < b)
#define all(c) c.begin(),c.end()
void YES(bool t=true) {cout<<(t?"YES":"NO")<<endl;}
void Yes(bool t=true) {cout<<(t?"Yes":"No")<<endl;}
void yes(bool t=true) {cout<<(t?"yes":"no")<<endl;}
void NO(bool t=true) {cout<<(t?"NO":"YES")<<endl;}
void No(bool t=true) {cout<<(t?"No":"Yes")<<endl;}
void no(bool t=true) {cout<<(t?"no":"yes")<<endl;}
template<class T> bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a = b; return 1; } return 0; }
#define UNIQUE(v) v.erase(std::unique(v.begin(), v.end()), v.end());
const ll inf = 1000000001;
const ll INF = (ll)1e18 + 1;
const long double pi = 3.1415926535897932384626433832795028841971L;
#define Sp(p) cout<<setprecision(25)<< fixed<<p<<endl;
// int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
// int dx2[8] = { 1,1,0,-1,-1,-1,0,1 }, dy2[8] = { 0,1,1,1,0,-1,-1,-1 };
vi dx = {0, 1, 0, -1}, dy = {-1, 0, 1, 0};
vi dx2 = { 1,1,0,-1,-1,-1,0,1 }, dy2 = { 0,1,1,1,0,-1,-1,-1 };
#define fio() cin.tie(0); ios::sync_with_stdio(false);
// const ll MOD = 1000000007;
const ll MOD = 998244353;
// #define mp make_pair
//#define endl '\n'

const int N = 3001;
vector<vector<pll>> G(N);

ll dist[N][N];
ll dp[2][N][N];
vll path(N);

void dfs(int now, int par, int root, ll sum) {
    dist[root][now] = sum;
    for (pll temp: G[now]) {
        if (temp.first == par) continue;
        dfs(temp.first, now, root, sum + temp.second);
    }
    path[root].push_back(now);
}

signed main() {
    fio();
    ll n, q, c;
    cin >> n >> q >> c;
    rep (i, n - 1) {
        int u, v, l;
        cin >> u >> v >> l;
        u--; v--;
        G[u].push_back(pll(v, l));
        G[v].push_back(pll(u, l));
    }

    rep (i, n) {
        dfs(i, -1, i, 0);
    }

    vector<short> x(q);
    rep (i, q) {
        cin >> x[i];
        x[i]--;
    }

    rep (i, 2) rep (j, q) rep (k, n) dp[i][j][k] = INF;

    dp[1][0][x[0]] = 0;
    // using P = pair<ll, array<short, 3>>;
    // priority_queue<P, vector<P>, greater<P>> pq;
    // pq.push(P(0, {1, 0, x[0]}));

    rep (i, q - 1) {
        rep (k, 2) {
            for (int j: path[x[i + 1]]) {
                ll cost = dp[k][i][j];
                if (k == 0) {
                    short ni = i, nj = j, nk = 1;
                    if (dp[nk][ni][nj] > cost + c) {
                        dp[nk][ni][nj] = cost + c;
                    }

                    ni = i + 1, nj = j, nk = 0;
                    if (dp[nk][ni][nj] > cost + dist[x[i]][x[i + 1]]) {
                        dp[nk][ni][nj] = cost + dist[x[i]][x[i + 1]];
                    }
                }
                if (k == 1) {
                    short ni = i + 1, nj = j, nk = 0;
                    if (dp[nk][ni][nj] > cost + dist[j][x[i + 1]]) {
                        dp[nk][ni][nj] = cost + dist[j][x[i + 1]];
                        // pq.push(P(dp[nk][ni][nj], {nk, ni, nj}));
                    }

                    if (j == x[i + 1]) {
                        short ni = i + 1, nj = j, nk = 1;
                        if (dp[nk][ni][nj] > cost) {
                            dp[nk][ni][nj] = cost;
                            // pq.push(P(dp[nk][ni][nj], {nk, ni, nj}));
                        }
                    }

                    for (pll temp: G[j]) {
                        short ni = i, nj = temp.first, nk = 1;
                        if (dist[nj][x[i + 1]] > dist[j][x[i + 1]]) continue;
                        if (dp[nk][ni][nj] > cost + temp.second) {
                            dp[nk][ni][nj] = cost + temp.second;
                            // pq.push(P(dp[nk][ni][nj], {nk, ni, nj}));
                        }
                    }
                }
            }
        }
    }
    // while (pq.size()) {
    //     P temp = pq.top();
    //     pq.pop();
    //     ll cost = temp.first;
    //     short i = temp.second[1], j = temp.second[2], k = temp.second[0];
    //     if (i == q - 1) continue;
    //     if (dp[k][i][j] < cost) continue;

    //     if (k == 0) {
    //     }
    //     if (k == 1) {
    //     }
    // }

    ll ans = INF;
    rep (k, 2) {
        rep (j, n) {
            chmin(ans, dp[k][q - 1][j]);
        }
    }
    cout << ans << endl;
}