#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>>>;

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

int main() {
    constexpr int64_t inf = 1e18;
    int64_t n, q, c;
    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.at(u).emplace_back(v, l);
        to.at(v).emplace_back(u, l);
    }
    vector<int> x(q);
    for (int i = 0; i < q; i++) {
        cin >> x.at(i);
        x.at(i)--;
    }
    vector dist(n, vector(n, int64_t()));
    for (int i = 0; i < n; i++) {
        dfs(to, dist.at(i), i, -1);
    }

    vector dp(q, vector(n, inf));
    dp.at(0).at(x.at(0)) = 0;
    int64_t mincost_prev = 0;
    for (int i = 1; i < q; i++) {
        int64_t mincost = inf;
        for (int j = 0; j < n; j++) {
            chmin(dp.at(i).at(j), dp.at(i - 1).at(j) + dist.at(x.at(i - 1)).at(x.at(i)));
            chmin(dp.at(i).at(j), mincost_prev + dist.at(x.at(i - 1)).at(j) + dist.at(j).at(x.at(i)));
/*            for (int k = 0; k < n; k++) {
                chmin(dp.at(i).at(j), dp.at(i - 1).at(k) + c + dist.at(k).at(j) + dist.at(j).at(x.at(i)));
                }*/
            chmin(dp.at(i).at(j), dp.at(i - 1).at(j) + c + dist.at(j).at(x.at(i)));
            chmin(mincost, dp.at(i).at(j));
        }
        mincost_prev = mincost;
    }
    cout << dp.at(q - 1).at(x.at(q - 1)) << endl;
}