#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <cassert>

#define debug_value(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << #x << "=" << x << endl;
#define debug(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << x << endl;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

using namespace std;
typedef long long ll;

struct edge{
    int to;
    ll cost;
};

const ll INF = 1e16;

int n, q;
ll c;
int x[3000];
vector<edge> G[3000];

ll dp[3005][3005];

void input(){
    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((edge){v, l});
        G[v].push_back((edge){u, l});
    }
    for(int i = 0; i < q; i++) {
        cin >> x[i]; x[i]--;
    }
    for(int i = 0; i < q; i++){
        for(int j = 0; j < n; j++){
            dp[i][j] = INF;
        }
    }
}

ll dist[3000];
ll cost[3000];
bool used[3000];

void clear(){
    for(int i = 0; i < n; i++) used[i] = false;
}

// x[idx]に行こうとしている
ll dfs(int v, int idx){
    used[v] = true;
    ll ans = INF;
    for(edge e: G[v]){
        if(!used[e.to]){
            dist[e.to] = dist[v]+e.cost;
            chmin(ans, dfs(e.to, idx));
        }
    }
    chmin(ans, cost[v]+dist[v]);
    chmin(dp[idx][v], ans);
    return ans;
}

void solve(){
    dp[0][x[0]] = 0;
    for(int i = 1; i < q; i++){
        clear();
        for(int j = 0; j < n; j++){
            if(j != x[i-1]){
                cost[j] = dp[i-1][j]+c;
            }else{
                cost[j] = dp[i-1][j];
            }
        }
        dist[x[i]] = 0;
        dfs(x[i], i);
        for(int j = 0; j < n; j++){
            chmin(dp[i][j], dp[i-1][j]+dist[x[i-1]]);
        }
    }
    cout << dp[q-1][x[q-1]] << endl;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << setprecision(10) << fixed;
    input();
    solve();
}