//
// AC solution (writer)
//

#include <bits/stdc++.h>

using namespace std;

using ll = long long;
constexpr ll INF = 1e18;

vector<vector<pair<int, int>>> e;

ll dist(int x, int p, int to) {
    if (x == to) return 0;
    ll ans = INF;
    for (auto &ep : e[x]) {
        if (ep.first == p) continue;
        ans = min(ans, ep.second + dist(ep.first, x, to));
    }
    return ans;
}

vector<ll> dp;

ll dfs(int x, int p, ll d, ll l) {
    dp[x] += min(d, l);
    for (auto &ep : e[x]) {
        if (ep.first == p) continue;
        dp[x] = min(dp[x], dfs(ep.first, x, ep.second + d, l));
    }
    return dp[x];
}

int main() {
    int n, q, c;
    cin >> n >> q >> c;
    e = vector<vector<pair<int, int>>>(n);
    for (int i = 0; i < n - 1; i++) {
        int u, v, l;
        cin >> u >> v >> l;
        u--, v--;
        e[u].emplace_back(v, l);
        e[v].emplace_back(u, l);
    }

    vector<int> x(q);
    for (int i = 0; i < q; i++) {
        cin >> x[i];
        x[i]--;
    }
    dp = vector<ll>(n, INF);
    dp[x[0]] = 0;
    for (int i = 1; i < q; i++) {
        ll l = dist(x[i], x[i], x[i - 1]);
        dfs(x[i], x[i], c, l);
    }
    cout << dp[x[q - 1]] << endl;

    return 0;
}