#include <bits/stdc++.h>
using namespace std;

template <typename T>
void chmin(T &a, T b) {
    if (b < a) {
        a = b;
    }
}

using graph = vector<vector<pair<int64_t, int64_t>>>;
using grid = vector<vector<int64_t>>;
using vec = vector<int64_t>;

constexpr int64_t inf = 1e18;
int64_t n, c;

void dfs(const graph &to, vector<int64_t> &dist, int v, int par) {
    for (auto [next, l] : to[v]) {
        if (next == par) continue;
        dist[next] = dist[v] + l;
        dfs(to, dist, next, v);
    }
}

void treedp(const graph &to, const grid &dist, const vec &prev, vec &next,
            vec &tele, int x0, int x1, int v, int par) {
    tele[v] = prev[v] + c + dist[v][x1];
    for (auto [child, _] : to[v]) {
        if (child == par) continue;
        treedp(to, dist, prev, next, tele, x0, x1, child, v);
        chmin(tele[v], tele[child]);
    }
    chmin(next[v], prev[v] + dist[x0][x1]);
    chmin(next[v], prev[x0] + dist[x0][v] + dist[v][x1]);
    chmin(next[v], tele[v]);
}

int main() {
    int64_t q;
    cin >> n >> q >> c;
    graph to(n);
    for (int i = 0; i < n - 1; i++) {
        int64_t u, v, l;
        cin >> u >> v >> l;
        u--; v--;
        to[u].emplace_back(v, l);
        to[v].emplace_back(u, l);
    }
    vector<int> x(q);
    for (int i = 0; i < q; i++) {
        cin >> x[i];
        x[i]--;
    }
    grid dist(n, vec(n));
    for (int i = 0; i < n; i++) {
        dfs(to, dist[i], i, -1);
    }

    grid dp(q, vec(n, inf));
    dp[0][x[0]] = 0;
    vec tele(n);
    for (int i = 1; i < q; i++) {
        treedp(to, dist, dp[i - 1], dp[i], tele, x[i - 1], x[i], x[i], -1);
    }
    cout << dp[q - 1][x[q - 1]] << endl;
}