#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 1000000000000000



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;
}


struct HLD{
	vector<int> sz,parent,depth,root,pos;
	vector<int> arr;
	HLD(vector<vector<int>> &E){
		sz.resize(E.size(),1);
		parent.resize(E.size(),0);
		depth.resize(E.size(),0);
		root.resize(E.size(),0);
		pos.resize(E.size(),0);
		
		dfs(0,-1,E);
		dfs2(0,-1,E,0);
	}
	
	void dfs(int now,int p,vector<vector<int>> &E){
		parent[now] = p;
		if(p==-1){
			depth[now] = 0;
		}
		else{
			depth[now] = depth[p]+1;
		}
		for(int i=0;i<E[now].size();i++){
			int to = E[now][i];
			if(to==p)continue;
			dfs(to,now,E);
			sz[now] += sz[to];
		}
	}
	
	void dfs2(int now,int p,vector<vector<int>> &E,int r){
		pos[now] = arr.size();
		arr.push_back(now);
		root[now] = r;
		int maxi = 0;
		int ind = -1;
		for(int i=0;i<E[now].size();i++){
			int to = E[now][i];
			if(to==p)continue;
			if(maxi<sz[to]){
				maxi = sz[to];
				ind = to;
			}
		}
		if(ind==-1)return;
		dfs2(ind,now,E,r);
		for(int i=0;i<E[now].size();i++){
			int to = E[now][i];
			if(to==p||to==ind)continue;
			dfs2(to,now,E,to);
		}
	}
	
	vector<pair<int,int>> query(int u,int v){
		vector<pair<int,int>> ret;
		int t = 0;
		while(root[u]!=root[v]){
			if(depth[root[u]] <= depth[root[v]]){
				ret.insert(ret.begin()+t,{pos[root[v]], pos[v]});
				v = parent[root[v]];
			}
			else{
				ret.insert(ret.begin()+t,{pos[u],pos[root[u]]});
				u = parent[root[u]];
				t++;
			}
		}
		ret.insert(ret.begin()+t,{pos[u],pos[v]});
		return ret;
	}
	
	int lca(int u,int v){
		for(;;v=parent[root[v]]){
			if(pos[u]>pos[v])swap(u,v);
			if(root[u]==root[v])return u;
		}
	}
	
	int get_distance(int u,int v){
		return depth[u] + depth[v] - 2 * depth[lca(u,v)];
	}
	
};
long long C;
void dfs(auto &E,auto &dp,auto &ndp,auto &dis,int now,int F,int P,int p=-1){
	
	ndp[now] = dp[now] + C + dis[now][P];
	if(F==now)ndp[now] -= C;
	
	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>>());
	vector EE(N,vector<int>());
	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);
		
		EE[u].push_back(v);
		EE[v].push_back(u);
	}
	
	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;
}