#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i=0; i<n; i++)
#define pb push_back
typedef long long ll;
typedef pair<int, ll> P1;
typedef pair<int, int> P2;

ll N, Q, C;
vector<P1> G[3010];
vector<vector<ll>> dists;
int x[3010];

vector<ll> bfs(int s) {
    queue<int> q;
    q.push(s);
    vector<ll> dist(N);
    rep(i, N) dist[i] = -1;
    dist[s] = 0;
    
    while (q.size()) {
        int v = q.front(); q.pop();
        rep(i, G[v].size()) {
            P1 p = G[v][i];
            int nv = p.first;
            ll w = p.second;
            if (dist[nv]==-1) {
                dist[nv] = dist[v]+w;
                q.push(nv);
            }
        }
    }
    
    return dist;
}

int ceil_pow2(int n) {
    int x = 0;
    while ((1U << x) < (unsigned int)(n)) x++;
    return x;
}

template <class S,
          S (*op)(S, S),
          S (*e)(),
          class F,
          S (*mapping)(F, S),
          F (*composition)(F, F),
          F (*id)()>
struct lazy_segtree {
  public:
    lazy_segtree() : lazy_segtree(0) {}
    lazy_segtree(int n) : lazy_segtree(std::vector<S>(n, e())) {}
    lazy_segtree(const std::vector<S>& v) : _n(int(v.size())) {
        log = ceil_pow2(_n);
        size = 1 << log;
        d = std::vector<S>(2 * size, e());
        lz = std::vector<F>(size, id());
        for (int i = 0; i < _n; i++) d[size + i] = v[i];
        for (int i = size - 1; i >= 1; i--) {
            update(i);
        }
    }

    void set(int p, S x) {
        assert(0 <= p && p < _n);
        p += size;
        for (int i = log; i >= 1; i--) push(p >> i);
        d[p] = x;
        for (int i = 1; i <= log; i++) update(p >> i);
    }

    S get(int p) {
        assert(0 <= p && p < _n);
        p += size;
        for (int i = log; i >= 1; i--) push(p >> i);
        return d[p];
    }

    S prod(int l, int r) {
        assert(0 <= l && l <= r && r <= _n);
        if (l == r) return e();

        l += size;
        r += size;

        for (int i = log; i >= 1; i--) {
            if (((l >> i) << i) != l) push(l >> i);
            if (((r >> i) << i) != r) push(r >> i);
        }

        S sml = e(), smr = e();
        while (l < r) {
            if (l & 1) sml = op(sml, d[l++]);
            if (r & 1) smr = op(d[--r], smr);
            l >>= 1;
            r >>= 1;
        }

        return op(sml, smr);
    }

    S all_prod() { return d[1]; }

    void apply(int p, F f) {
        assert(0 <= p && p < _n);
        p += size;
        for (int i = log; i >= 1; i--) push(p >> i);
        d[p] = mapping(f, d[p]);
        for (int i = 1; i <= log; i++) update(p >> i);
    }
    void apply(int l, int r, F f) {
        assert(0 <= l && l <= r && r <= _n);
        if (l == r) return;

        l += size;
        r += size;

        for (int i = log; i >= 1; i--) {
            if (((l >> i) << i) != l) push(l >> i);
            if (((r >> i) << i) != r) push((r - 1) >> i);
        }

        {
            int l2 = l, r2 = r;
            while (l < r) {
                if (l & 1) all_apply(l++, f);
                if (r & 1) all_apply(--r, f);
                l >>= 1;
                r >>= 1;
            }
            l = l2;
            r = r2;
        }

        for (int i = 1; i <= log; i++) {
            if (((l >> i) << i) != l) update(l >> i);
            if (((r >> i) << i) != r) update((r - 1) >> i);
        }
    }

  private:
    int _n, size, log;
    std::vector<S> d;
    std::vector<F> lz;

    void update(int k) { d[k] = op(d[2 * k], d[2 * k + 1]); }
    void all_apply(int k, F f) {
        d[k] = mapping(f, d[k]);
        if (k < size) lz[k] = composition(f, lz[k]);
    }
    void push(int k) {
        all_apply(2 * k, lz[k]);
        all_apply(2 * k + 1, lz[k]);
        lz[k] = id();
    }
};

ll op(ll x, ll y) {return min(x, y);}
ll e() {return 1000000000000000000;}
ll mapping(ll f, ll x) {return min(f, x);}
ll composition(ll f, ll g) {return min(f, g);}
ll id() {return 1000000000000000000;}

int par[3010], siz[3010], depth[3010];

int dfs1(int v, int pv, int d) {
    par[v] = pv;
    siz[v] = 1;
    depth[v] = d;
    rep(i, G[v].size()) {
        int nv = G[v][i].first;
        if (nv==pv) continue;
        siz[v] += dfs1(nv, v, d+1);
    }
    return siz[v];
}

int in_order[3010], top[3010];
int in_order_now;

void dfs2(int v, int pv, int top_node) {
    in_order[v] = in_order_now;
    in_order_now++;
    top[v] = top_node;
    if (siz[v]==1) return;
    int M = 0;
    int heavy_node = -1;
    rep(i, G[v].size()) {
        int nv = G[v][i].first;
        if (nv==pv) continue;
        if (siz[nv]>M) {
            M = siz[nv];
            heavy_node = nv;
        }
    }
    dfs2(heavy_node, v, top_node);
    rep(i, G[v].size()) {
        int nv = G[v][i].first;
        if (nv==pv) continue;
        if (nv!=heavy_node) dfs2(nv, v, nv);
    }
}

vector<P2> query(int u, int v) {
    vector<P2> res;
    while (top[u]!=top[v]) {
        if (depth[top[u]]<=depth[top[v]]) {
            res.pb(P2(in_order[top[v]], in_order[v]));
            v = par[top[v]];
        }
        else {
            res.pb(P2(in_order[top[u]], in_order[u]));
            u = par[top[u]];
        }
    }
    res.pb(P2(min(in_order[u], in_order[v]), max(in_order[u], in_order[v])));
    return res;
}

int main() {
    //ループ変数が被っていないか?
    //制約を確認しているか?
    //変数のtypoがないか?
    cin.tie(0); ios::sync_with_stdio(false);
    cin >> N >> Q >> C;
    rep(i, N-1) {
        int u, v; cin >> u >> v;
        ll l; cin >> l;
        G[u-1].pb(P1(v-1, l));
        G[v-1].pb(P1(u-1, l));
    }
    rep(i, N) dists.pb(bfs(i));
    
    rep(i, Q) cin >> x[i];
    rep(i, Q) x[i]--;
    
    dfs1(0, -1, 0);
    dfs2(0, -1, 0);
    lazy_segtree<ll, op, e, ll, mapping, composition, id> lst1(N);
    lst1.set(in_order[x[0]], 0);
    
    for (int i=1; i<Q; i++) {
        lazy_segtree<ll, op, e, ll, mapping, composition, id> lst2(N);
        
        rep(j, N) {
            lst2.apply(in_order[j], in_order[j]+1, lst1.get(j)+dists[x[i-1]][x[i]]);
            vector<P2> section = query(j, x[i]);
            ll v = lst1.get(in_order[j])+min(C, dists[x[i-1]][j])+dists[j][x[i]];
            
            rep(k, section.size()) {
                ll l = section[k].first, r = section[k].second;
                lst2.apply(l, r+1, v);
            }
        }
        
        swap(lst1, lst2);
    }
    
    cout << lst1.all_prod() << endl;
}