#pragma target("avx2")
#pragma optimize("O3")
#pragma optimize("unroll-loops")

#include <stdio.h>
#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 100000000000000000



vector<long long> get(int start,auto &E){
	vector<long long> dis(E.size(),Inf);
	dis[start] = 0;
	queue<int> Q;
	Q.push(start);
	
	while(Q.size()>0){
		int u = Q.front();
		Q.pop();
		rep(i,E[u].size()){
			int v = E[u][i].first;
			if(dis[v]!=Inf)continue;
			dis[v] = dis[u] + E[u][i].second;
			Q.push(v);
		}
	}
	
	return dis;
}

long long C;
void dfs(auto &E,auto &dp,auto &ndp,auto &dis,int now,int F,int P,int p=-1){
	
	if(F!=now)ndp[now] = min(ndp[now],dp[now] + C + dis[now][P]);
	else ndp[now] = min(ndp[now],dp[now] + dis[now][P]);
	
	rep(i,E[now].size()){
		int to = E[now][i].first;
		if(to==p)continue;
		dfs(E,dp,ndp,dis,to,F,P,now);
		ndp[now] = min(ndp[now],ndp[to]);
	}
}

int main(){
	
	int N,Q;
	
	cin>>N>>Q>>C;
	
	vector E(N,vector<pair<int,long long>>());
	rep(i,N-1){
		int u,v,l;
		scanf("%d %d %d",&u,&v,&l);
		
		u--;v--;
		E[u].emplace_back(v,l);
		E[v].emplace_back(u,l);
	}
	
	vector<int> x(Q);
	rep(i,Q){
		scanf("%d",&x[i]);
		x[i]--;
	}
	
	vector dis(N,vector<long long>());
	
	rep(i,N){
		dis[i] = get(i,E);
	}
	
	vector<long long> dp(N,Inf);
	
	dp[x[0]] = 0LL;
	
	rep(i,Q-1){
		vector<long long> ndp(N,Inf);

		dfs(E,dp,ndp,dis,x[i+1],x[i],x[i+1]);
		
		rep(j,N){
			ndp[j] = min(ndp[j],dp[j] + dis[x[i]][x[i+1]]);
		}
		
		swap(dp,ndp);
		
		
	}
	
	long long ans = Inf;
	rep(i,N)ans = min(ans,dp[i]);
	
	cout<<ans<<endl;
	
	
    return 0;
}