#include <bits/stdc++.h>
//#include <chrono>
#pragma GCC optimize("O3")
using namespace std;
#define reps(i,s,n) for(int i = s; i < n; i++)
#define rep(i,n) reps(i,0,n)
#define Rreps(i,n,e) for(int i = n - 1; i >= e; --i)
#define Rrep(i,n) Rreps(i,n,0)
#define ALL(a) a.begin(), a.end()

using ll = long long;
using vec = vector<ll>;
using mat = vector<vec>;

ll N,M,H,W,Q,K,A,B;
string S;
using P = pair<ll, ll>;
const ll INF = (1LL<<60);

template<class T> bool chmin(T &a, const T &b){
    if(a > b) {a = b; return true;}
    else return false;
}
template<class T> bool chmax(T &a, const T &b){
    if(a < b) {a = b; return true;}
    else return false;
}
template<class T> void print_vector(std::vector<T> v,bool endline = true){
    if(!v.empty()){
        for(std::size_t i{}; i<v.size()-1; ++i) std::cout<<v[i]<<" ";
        std::cout<<v.back();
    }
    if(endline) std::cout<<std::endl;
}

struct edge{
        int to, cost;
        edge(int a, int b) : to(a), cost(b){}
    };
using ve = vector<edge>;

int s, t;
ve course;
vector<ve> G(3010);
bool dfs(int p, int v){
    if(v == t) return true;
    for(const edge &e : G[v]){
        if(e.to != p){
            course.push_back(e);
            if(dfs(v, e.to)) return true;
            else course.pop_back();
        }
    }
    return false;
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cin>>N>>Q>>K;
    vec dp(N, INF);
    ll dp_min, temp_cost, range_sum;
    rep(i, N - 1){
        ll u, v, l; cin>>u>>v>>l; --u; --v;
        G[u].emplace_back(v, l);
        G[v].emplace_back(u, l);
    }
    cin>>t; --t;
    dp[t] = 0;
    dp_min = 0;
    reps(i, 1, Q){
        s = t; cin>>t; --t;
        temp_cost = dp_min; range_sum = 0;

        dfs(-1, s);
        for(const edge &e : course){
            temp_cost += e.cost; range_sum += e.cost;
            chmin(temp_cost, dp[e.to] + K);
            chmin(dp[e.to], temp_cost - range_sum);
        }
        course.clear();

        dp_min = INF;
        rep(v, N) {
            if(dp[v] != INF) dp[v] += range_sum;
            chmin(dp_min, dp[v]);
        }
    }
    cout<<dp_min<<endl;
}