#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define R cin>>
#define ll long long
#define ln cout<<'\n'
#define in(a) insert(a)
#define pb(a) push_back(a)
#define pd(a) printf("%.10f\n",a)
#define mem(a) memset(a,0,sizeof(a))
#define all(c) (c).begin(),(c).end()
#define iter(c) __typeof((c).begin())
#define rrep(i,n) for(ll i=(ll)(n)-1;i>=0;i--)
#define REP(i,m,n) for(ll i=(ll)(m);i<(ll)(n);i++)
#define rep(i,n) REP(i,0,n)
#define tr(it,c) for(iter(c) it=(c).begin();it!=(c).end();it++)
ll check(ll n,ll m,ll x,ll y){return x>=0&&x<n&&y>=0&&y<m;}void pr(){ln;}
template<class A,class...B>void pr(const A &a,const B&...b){cout<<a<<(sizeof...(b)?" ":"");pr(b...);}
template<class A>void PR(A a,ll n){rep(i,n)cout<<(i?" ":"")<<a[i];ln;}
const ll MAX=1e9+7,MAXL=1LL<<61,dx[8]={-1,0,1,0,-1,-1,1,1},dy[8]={0,1,0,-1,-1,1,1,-1};
typedef pair<ll,ll> P;

ll dep[200010],dep2[200010];
ll par[200010][20];
vector<P> v[200010];
void dfs(ll x,ll y,ll d){
  dep[x]=d;
  for(int i=0; i<v[x].size(); i++){
    ll z=v[x][i].F;if(z==y) continue;
    par[z][0]=x;dfs(z,x,d+1);
  }
}
void dfs2(ll x,ll y,ll d){
  dep2[x]=d;
  for(int i=0; i<v[x].size(); i++){
    ll z=v[x][i].F;if(z==y) continue;
    dfs2(z,x,d+v[x][i].S);
  }
}
int lca(int a,int b){
  if(dep[a]<dep[b]) swap(a,b);
  for(int i=0; i<20; i++){
    if((dep[a]-dep[b])&(1<<i)) a=par[a][i];
  }
  if(a==b) return a;
  for(int i=19;i>=0;i--){
    if(par[a][i]!=par[b][i]) a=par[a][i],b=par[b][i];
  }
  return par[a][0];
}

int n;
void init() {
  memset(par,0,sizeof(par));
  dfs(0,-1,0);
  for(int i=0; i<19; i++)for(int j=0; j<n; j++) par[j][i+1]=par[par[j][i]][i];
  dfs2(0,-1,0);
}
ll D(int x,int y) {
  return dep2[x]+dep2[y]-dep2[lca(x,y)]*2;
}

ll dp[3333][3333];

void Main() {
  ll m,c;
  cin >> n >> m >> c;
  rep(i,n-1) {
    ll x,y,z;
    cin >> x >> y >> z;
    x--,y--;
    v[x].pb(P(y,z));
    v[y].pb(P(x,z));
  }
  ll a[m];
  rep(i,m) {
    cin >> a[i];
    a[i]--;
  }
  init();
  rep(i,m)rep(j,n) dp[i][j]=MAXL;
  dp[0][a[0]]=0;
  REP(i,1,m) {
    ll M=MAXL;
    rep(j,n) {
      dp[i][j]=min(dp[i][j],dp[i-1][j]+D(a[i-1],a[i]));
      dp[i][j]=min(dp[i][j],dp[i-1][j]+(j!=a[i-1]?c:0)+D(j,a[i]));
      dp[i][a[i]]=min(dp[i][a[i]],dp[i-1][j]+(j!=a[i-1]?c:0)+D(j,a[i]));
      M=min(M,dp[i-1][j]);
    }
    rep(j,n) dp[i][j]=min(dp[i][j],M+D(a[i-1],j)+D(j,a[i]));
  }
  ll ans=MAXL;
  rep(i,n) ans=min(ans,dp[m-1][i]);
  pr(ans);
}

int main(){ios::sync_with_stdio(0);cin.tie(0);Main();return 0;}