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

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].emplace_back(l, v);
        edge[v].emplace_back(l, u);
    }
    vector<vector<long long>> dist(n, vector<long long>(n));
    for (int i = 0; i < n; ++i) {
        dfs(i, -1, 0, dist[i]);
    }
    vector<long long> dp(n, LM);
    int prev;
    cin >> prev;
    --prev;
    dp[prev] = 0;
    for (int i = 1; i < q; ++i) {
        int x;
        cin >> x;
        --x;
        dfs(x, -1, c, dist[prev][x], dp);
        prev = x;
    }
    long long ans = LM;
    for (int i = 0; i < n; ++i) {
        ans = min(ans, dp[i]);
    }
    cout << ans << '\n';
    return 0;
}