#include<bits/stdc++.h>
using namespace std;
using P = pair<int, int>;
const long long LM = 1LL << 60;


vector<vector<P>> edge;

void dfs(int p, int par, long long l, vector<long long>& dist) {
    dist[p] = l;
    for (auto& e : edge[p]) {
        if (e.second == par) continue;
        dfs(e.second, p, l + e.first, dist);
    }
}


long long dfs(int p, int par, vector<long long>& d) {
    long long mi = d[p];
    for (auto& e : edge[p]) {
        if (e.second == par) continue;
        mi = min(mi, dfs(e.second, p, d) + e.first);
    }
    return d[p] = mi;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    int n, q, c;
    cin >> n >> q >> c;
    edge = vector<vector<P>>(n);
    for (int i = 0; i < n - 1; ++i) {
        int u, v, l;
        cin >> u >> v >> l;
        --u;
        --v;
        edge[u].push_back({l, v});
        edge[v].push_back({l, u});
    }
    vector<int> x(q);
    for (int i = 0; i < q; ++i) {
        cin >> x[i];
        --x[i];
    }
    vector<vector<long long>> dist(n, vector<long long>(n, LM));
    for (int i = 0; i < n; ++i) {
        dfs(i, -1, 0, dist[i]);
    }
    vector<long long> dp(n, LM);
    dp[x[0]] = 0;
    for (int i = 1; i < q; ++i) {
        vector<long long> d(n, LM);
        for (int j = 0; j < n; ++j) {
            d[j] = min(d[j], dp[j] + c);
            d[x[i - 1]] = min(d[x[i - 1]], dp[j]);
        }
        dfs(x[i], -1, d);
        for (int j = 0; j < n; ++j) {
            dp[j] = min(dp[j] + dist[x[i - 1]][x[i]], d[j] + dist[j][x[i]]);
        }
    }
    long long ans = LM;
    for (int i = 0; i < n; ++i) {
        ans = min(ans, dp[i]);
    }
    cout << ans << '\n';

    return 0;
}