#line 2 "cpplib/util/template.hpp"
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("avx2")
#include<bits/stdc++.h>
using namespace std;
struct __INIT__{__INIT__(){cin.tie(0);ios::sync_with_stdio(false);cout<<fixed<<setprecision(15);}}__INIT__;
typedef long long lint;
#define INF (1LL<<60)
#define IINF (1<<30)
#define EPS (1e-10)
#define endl ('\n')
typedef vector<lint> vec;
typedef vector<vector<lint>> mat;
typedef vector<vector<vector<lint>>> mat3;
typedef vector<string> svec;
typedef vector<vector<string>> smat;
template<typename T>using V=vector<T>;
template<typename T>using VV=V<V<T>>;
template<typename T>inline void output(T t){bool f=0;for(auto i:t){cout<<(f?" ":"")<<i;f=1;}cout<<endl;}
template<typename T>inline void output2(T t){for(auto i:t)output(i);}
template<typename T>inline void debug(T t){bool f=0;for(auto i:t){cerr<<(f?" ":"")<<i;f=1;}cerr<<endl;}
template<typename T>inline void debug2(T t){for(auto i:t)output(i);}
#define loop(n) for(long long _=0;_<(long long)(n);++_)
#define rep(i,...) for(auto i:range(__VA_ARGS__)) 
#define rrep(i,...) for(auto i:reversed(range(__VA_ARGS__)))
#define repi(i,a,b) for(lint i=lint(a);i<(lint)(b);++i)
#define rrepi(i,a,b) for(lint i=lint(b)-1;i>=lint(a);--i)
#define irep(i) for(lint i=0;;++i)
inline vector<long long> range(long long n){if(n<=0)return vector<long long>();vector<long long>v(n);iota(v.begin(),v.end(),0LL);return v;}
inline vector<long long> range(long long a,long long b){if(b<=a)return vector<long long>();vector<long long>v(b-a);iota(v.begin(),v.end(),a);return v;}
inline vector<long long> range(long long a,long long b,long long c){if((b-a+c-1)/c<=0)return vector<long long>();vector<long long>v((b-a+c-1)/c);for(int i=0;i<(int)v.size();++i)v[i]=i?v[i-1]+c:a;return v;}
template<typename T>inline T reversed(T v){reverse(v.begin(),v.end());return v;}
#define all(n) begin(n),end(n)
template<typename T,typename E>bool chmin(T& s,const E& t){bool res=s>t;s=min<T>(s,t);return res;}
template<typename T,typename E>bool chmax(T& s,const E& t){bool res=s<t;s=max<T>(s,t);return res;}
const vector<lint> dx={1,0,-1,0,1,1,-1,-1};
const vector<lint> dy={0,1,0,-1,1,-1,1,-1};
#define SUM(v) accumulate(all(v),0LL)
template<typename T,typename ...Args>auto make_vector(T x,int arg,Args ...args){if constexpr(sizeof...(args)==0)return vector<T>(arg,x);else return vector(arg,make_vector<T>(x,args...));}
#define extrep(v,...) for(auto v:__MAKE_MAT__({__VA_ARGS__}))
vector<vector<long long>> __MAKE_MAT__(vector<long long> v){if(v.empty())return vector<vector<long long>>(1,vector<long long>());long long n=v.back();v.pop_back();vector<vector<long long>> ret;vector<vector<long long>> tmp=__MAKE_MAT__(v);for(auto e:tmp)for(long long i=0;i<n;++i){ret.push_back(e);ret.back().push_back(i);}return ret;}
//#include "../graph_tree/graph_template.hpp"
template<typename T,typename E>ostream& operator<<(ostream& out,pair<T,E>v){out<<"("<<v.first<<","<<v.second<<")";return out;}
#line 5 "cpplib/graph_tree/graph_template.hpp"
/**
 * @brief グラフテンプレート
 */

using graph=std::vector<std::vector<int>>;
template<typename T>
using graph_w=std::vector<std::vector<std::pair<int,T>>>;

graph load_graph(int n,int m){graph g(n);for(int i=0;i<m;++i){int s,t;std::cin>>s>>t;--s;--t;g[s].push_back(t);g[t].push_back(s);}return g;}
graph load_digraph(int n,int m){graph g(n);for(int i=0;i<m;++i){int s,t;std::cin>>s>>t;--s;--t;g[s].push_back(t);}return g;}
graph load_graph0(int n,int m){graph g(n);for(int i=0;i<m;++i){int s,t;std::cin>>s>>t;g[s].push_back(t);g[t].push_back(s);}return g;}
graph load_digraph0(int n,int m){graph g(n);for(int i=0;i<m;++i){int s,t;std::cin>>s>>t;g[s].push_back(t);}return g;}
graph load_tree(int n){graph g(n);for(int i=0;i<n-1;++i){int s,t;std::cin>>s>>t;--s;--t;g[s].push_back(t);g[t].push_back(s);}return g;}
graph load_tree0(int n){graph g(n);for(int i=0;i<n-1;++i){int s,t;std::cin>>s>>t;g[s].push_back(t);g[t].push_back(s);}return g;}
graph load_treep(int n){graph g(n);for(int i=0;i<n-1;++i){int t;std::cin>>t;g[i+1].push_back(t);g[t].push_back(i+1);}return g;}
template<typename T>graph_w<T> load_graph_weight(int n,int m){graph_w<T> g(n);for(int i=0;i<m;++i){int s,t;T u;std::cin>>s>>t>>u;--s;--t;g[s].emplace_back(t,u);g[t].emplace_back(s,u);}return g;}
template<typename T>graph_w<T> load_digraph_weight(int n,int m){graph_w<T> g(n);for(int i=0;i<m;++i){int s,t;T u;std::cin>>s>>t>>u;--s;--t;g[s].emplace_back(t,u);}return g;}
template<typename T>graph_w<T> load_graph0_weight(int n,int m){graph_w<T> g(n);for(int i=0;i<m;++i){int s,t;T u;std::cin>>s>>t>>u;g[s].emplace_back(t,u);g[t].emplace_back(s,u);}return g;}
template<typename T>graph_w<T> load_digraph0_weight(int n,int m){graph_w<T> g(n);for(int i=0;i<m;++i){int s,t;T u;std::cin>>s>>t>>u;g[s].emplace_back(t,u);}return g;}
template<typename T>graph_w<T> load_tree_weight(int n){graph_w<T> g(n);for(int i=0;i<n-1;++i){int s,t;T u;std::cin>>s>>t>>u;--s;--t;g[s].emplace_back(t,u);g[t].emplace_back(s,u);}return g;}
template<typename T>graph_w<T> load_tree0_weight(int n){graph_w<T> g(n);for(int i=0;i<n-1;++i){int s,t;T u;std::cin>>s>>t>>u;g[s].emplace_back(t,u);g[t].emplace_back(s,u);}return g;}
template<typename T>graph_w<T> load_treep_weight(int n){graph_w<T> g(n);for(int i=0;i<n-1;++i){int t;T u;std::cin>>t>>u;g[i+1].emplace_back(t,u);g[t].emplace_back(i+1,u);}return g;}
#line 4 "cpplib/graph_tree/lca_short.hpp"

/**
 * @brief LCA(HL分解)&amp;lt;O(N),O(logN)&amp;gt;
 */

struct lca{
    graph g;
    std::vector<int>sz,in,out,nxt,par,par2;
    lca(const graph& g,int s):g(g){
        int n=g.size();
        sz.resize(n,0);
        in.resize(n,0);
        out.resize(n,0);
        nxt.resize(n,s);
        par.resize(n,s);
        par2.resize(n,s);
        dfs_sz(s,-1);
        dfs_hld(s,-1);
    }
    void dfs_sz(int v,int p) {
        sz[v] = 1;
        for(auto &u: g[v]) {
            if(p==u)continue;
            dfs_sz(u,v);
            sz[v]+=sz[u];
            if(sz[u]>sz[g[v][0]])std::swap(u,g[v][0]);
        }
    }
    void dfs_hld(int v,int p) {
        static int t=0;
        in[v]=t++;
        for(auto u: g[v]){
            if(p==u)continue;
            nxt[u]=(u==g[v][0]?nxt[v]:u);
            par[u]=(u==g[v][0]?par[v]:v);
            par2[u]=v;
            dfs_hld(u,v);
        }
        out[v] = t;
    }
    int query(int s,int t){
        while(nxt[s]!=nxt[t]){
			if(sz[nxt[s]]>sz[nxt[t]])t=par[t];
			else s=par[s];
		}
        return sz[s]>sz[t]?s:t;
    }
    int distance(int s,int t){
		int res=0;
		while(nxt[s]!=nxt[t]){
			if(sz[nxt[s]]>sz[nxt[t]]){
				res+=in[t]-in[nxt[t]]+1;
				t=par[t];
			}
			else {
				res+=in[s]-in[nxt[s]]+1;
				s=par[s];
			}
		}
		return res+std::abs(in[s]-in[t]);
	}
    std::vector<int>path(int s,int t){
        int l=query(s,t);
        vector<int>p,q;
        while(s!=l){
            p.push_back(s);
            s=par2[s];
        }
        while(t!=l){
            q.push_back(t);
            t=par2[t];
        }
        p.push_back(l);
        p.insert(p.end(),q.rbegin(),q.rend());
        return p;
    }
};
#line 3 "code.cpp"
int main(){
    lint n,q,c;
    cin>>n>>q>>c;
    vector<vector<lint>> dist(n,vector<lint>(n,0));
    vector<vector<int>> g(n);
    vector<vector<pair<lint,lint>>>v(n);
    rep(i,n-1){
        lint s,t,l;
        cin>>s>>t>>l;
        s--;t--;
        g[s].push_back(t);
        g[t].push_back(s);
        v[s].emplace_back(t,l);
        v[t].emplace_back(s,l);
        dist[s][t]=l;
        dist[t][s]=l;
    }
    lca lca(g,0);
    vector<int>x(q);
    rep(i,q)cin>>x[i];
    vector<lint>cnt(n,INF);
    cnt[x[0]-1]=0;
    lint cnt2=0;
    rep(i,q-1){
        int s=x[i]-1,t=x[i+1]-1;
        auto d=lca.path(s,t);
        lint mn=*min_element(all(cnt));
        rep(j,d.size()){
            cnt[d[j]]=min(mn,cnt[d[j]]+c)-cnt2;
            chmin(mn,cnt[d[j]]+cnt2);
            if(j<(int)d.size()-1){
                cnt2+=dist[d[j]][d[j+1]];
                mn+=dist[d[j]][d[j+1]];
            }
            // rep(k,n){
            //     cerr<<cnt[k]+cnt2<<" \n"[k==n-1];
            // }
        }
        rep(j,n)cnt[j]+=cnt2;
        cnt2=0;
    }
    cout<<*min_element(all(cnt))<<endl;
}