#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int MN = 3500;
vector<ll> T(MN, 0);
ll INF = (1LL << 60);
struct ED {
	int to;
	ll cost;
};
struct TP {
	ll m1 = INF;ll m2 = INF;
	void add(ll x) {
		if (x < m1) {
			m2 = m1;m1 = x;
		} else {
			m2 = min(m2, x);
		}
	}
	ll get(ll x) {
		return (x != m1 ? m1 : m2);
	}
};
vector<int> PAR(MN, 0);
vector<vector<ED>> G(MN);
vector<vector<ll>> D(MN, vector<ll> (MN, -1));
vector<ll> dp1, dp2;
void dfs(int v, int par) {
	dp1[v] = T[v];
	PAR[v] = par;
	for (auto nv : G[v]) {
		if (nv.to == par) continue;
		dfs(nv.to, v);
		dp1[v] = min(dp1[v], min(nv.cost + T[nv.to], nv.cost + dp1[nv.to]));
	}
}
void dfs2(int v, int par) {
	TP tp;
	for (auto nv : G[v]) {
		if (nv.to == par) {
			tp.add(min(nv.cost + T[nv.to], nv.cost + dp2[v]));
		} else {
			tp.add(min(nv.cost + T[nv.to], nv.cost + dp1[nv.to]));
		}
	}
	for (auto nv : G[v]) {
		if (nv.to == par) continue;
		dp2[nv.to] = T[v];
		ll value = min(nv.cost + T[nv.to], nv.cost + dp1[nv.to]);
		dp2[nv.to] = min(dp2[nv.to], tp.get(value));
		dfs2(nv.to, v);
	}
}
vector<ll> solve(int N) {
	dp1.assign(N, INF);
	dp2.assign(N, INF);
	dfs(0, 0);
	dfs2(0, 0);
	vector<ll> ans(N, INF);
	for (int v = 0;v < N;v++) {
		ans[v] = T[v];
		for (auto nv : G[v]) {
			ans[v] = min(ans[v], nv.cost + T[nv.to]);
			if (nv.to == PAR[v]) {
				ans[v] = min(ans[v], nv.cost + dp2[v]);
			} else {
				ans[v] = min(ans[v], nv.cost + dp1[nv.to]);
			}
		}
	}
	return ans;
}
int main() {
	int N, Q;ll C;cin >> N >> Q >> C;
	for (int i = 0;i < N - 1;i++) {
		int u, v;ll l;cin >> u >> v >> l;
		u--;v--;
		G[u].push_back({v, l});
		G[v].push_back({u, l});
	}
	vector<int> X(Q+1, -1);
	for (int i = 1;i <= Q;i++) cin >> X[i],X[i]--;
	for (int v = 0;v < N;v++) {
		D[v][v] = 0;
		queue<int> pq;
		pq.push(v);
		while (!pq.empty()) {
			int t = pq.front();pq.pop();
			for (auto nv : G[t]) {
				if (D[v][nv.to] == -1) {
					D[v][nv.to] = D[v][t] + nv.cost;
					pq.push(nv.to);
				}

			} 
		}
	}
	vector<ll> dp(N, INF);
	for (int v = 0;v < N;v++) {
		int s = X[1];int t = X[2];
		dp[v] = D[s][v] + D[v][t];
	}
	for (int i = 3;i <= Q;i++) {
		int s = X[i - 1];
		int t = X[i];
		vector<ll> ndp(N, INF);
		ll mins = INF;
		for (int v = 0;v < N;v++) {
			T[v] = dp[v];
			mins = min(mins, dp[v]);
		}
		for (int v = 0;v < N;v++) ndp[v] = D[s][v] + D[v][t] + mins;
		auto res = solve(N);
		for (int v = 0;v < N;v++) {
			ndp[v] = min(ndp[v], res[v] + D[v][t] + C);
			ndp[v] = min(ndp[v], dp[v] + D[s][t]);
		}
		swap(dp, ndp);
	}
	ll ans = INF;
	for (int v = 0;v < N;v++) ans = min(ans, dp[v]);
	cout << ans << endl;
}