#include <limits>
#include <initializer_list>
#include <utility>
#include <bitset>
#include <tuple>
#include <type_traits>
#include <functional>
#include <string>
#include <array>
#include <deque>
#include <list>
#include <queue>
#include <stack>
#include <vector>
#include <map>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <iterator>
#include <algorithm>
#include <complex>
#include <random>
#include <numeric>
#include <iostream>
#include <iomanip>
#include <sstream>
#include <regex>
#include <cassert>
#include <cstddef>
#include <variant>

#define endl codeforces

#define ALL(v) std::begin(v), std::end(v)
#define ALLR(v) std::rbegin(v), std::rend(v)

using ll = std::int64_t;
using ull = std::uint64_t;
using pii = std::pair<int, int>;
using tii = std::tuple<int, int, int>;
using pll = std::pair<ll, ll>;
using tll = std::tuple<ll, ll, ll>;
using size_type = ssize_t;
template <typename T> using vec = std::vector<T>;
template <typename T> using vvec = vec<vec<T>>;

template <typename T> const T& var_min(const T &t) { return t; }
template <typename T> const T& var_max(const T &t) { return t; }
template <typename T, typename... Tail> const T& var_min(const T &t, const Tail&... tail) { return std::min(t, var_min(tail...)); }
template <typename T, typename... Tail> const T& var_max(const T &t, const Tail&... tail) { return std::max(t, var_max(tail...)); }
template <typename T, typename... Tail> void chmin(T &t, const Tail&... tail) { t = var_min(t, tail...); }
template <typename T, typename... Tail> void chmax(T &t, const Tail&... tail) { t = var_max(t, tail...); }

template <typename T, std::size_t Head, std::size_t... Tail> 
struct multi_dim_array { using type = std::array<typename multi_dim_array<T, Tail...>::type, Head>; };

template <typename T, std::size_t Head> 
struct multi_dim_array<T, Head> { using type = std::array<T, Head>; };

template <typename T, std::size_t... Args> using mdarray = typename multi_dim_array<T, Args...>::type;

template <typename T, typename F, typename... Args> 
void fill_seq(T &t, F f, Args... args) { 
    if constexpr (std::is_invocable<F, Args...>::value) { 
        t = f(args...); 
    } else { 
        for (size_type i = 0; i < t.size(); i++) fill_seq(t[i], f, args..., i); 
    } 
}

template <typename T> vec<T> make_v(size_type sz) { return vec<T>(sz); }

template <typename T, typename... Tail> 
auto make_v(size_type hs, Tail&&... ts) { 
    auto v = std::move(make_v<T>(std::forward<Tail>(ts)...)); 
    return vec<decltype(v)>(hs, v); 
}

namespace init__ { 
struct InitIO { 
    InitIO() { 
        std::cin.tie(nullptr); 
        std::ios_base::sync_with_stdio(false); 
        std::cout << std::fixed << std::setprecision(30); 
    } 
} init_io; 
}

template <typename T>
T ceil_pow2(T bound) {
    T ret = 1;
    while (ret < bound) ret *= 2;
    return ret;
}

template <typename T>
T ceil_div(T a, T b) { return a / b + !!(a % b); }



namespace graph {

using Node = ll;
using Weight = ll;
using Edge = std::pair<Node, Weight>;

template <bool Directed>
struct Graph : public vvec<Edge> {
    using vvec<Edge>::vvec;

    void add_edge(Node f, Node t, Weight w = 1) {
        (*this)[f].emplace_back(t, w);
        if (!Directed) (*this)[t].emplace_back(f, w);
    }

    Graph<Directed> build_inv() const {
        Graph<Directed> ret(this->size());
        for (Node i = 0; i < this->size(); i++) {
            for (const Edge &e : (*this)[i]) {
                Node j;
                Weight w;
                std::tie(j, w) = e;
                if (!Directed && j < i) continue;
                ret.add_edge(j, i, w);
            }
        }

        return ret;
    }
};

template <typename Iterator>
class dst_iterator {
    Iterator ite;

public:
    dst_iterator(Iterator ite) : ite(ite) { }

    bool operator ==(const dst_iterator<Iterator> &oth) const {
        return ite == oth.ite;
    }

    bool operator !=(const dst_iterator<Iterator> &oth) const {
        return !(*this == oth);
    }

    bool operator <(const dst_iterator<Iterator> &oth) const {
        return ite < oth.ite;
    }

    bool operator >(const dst_iterator<Iterator> &oth) const {
        return ite > oth.ite;
    }

    bool operator <=(const dst_iterator<Iterator> &oth) const {
        return ite <= oth.ite;
    }

    bool operator >=(const dst_iterator<Iterator> &oth) const {
        return ite >= oth.ite;
    }

    const Node& operator *() {
        return ite->first;
    }

    const Node& operator *() const {
        return ite->first;
    }

    dst_iterator operator ++() {
        ++ite;
        return ite;
    }
};

class dst_iteration {
    using ite_type = vec<Edge>::const_iterator;
    const vec<Edge> &edges;

public:
    dst_iteration(const vec<Edge> &edges) : edges(edges) { }

    auto begin() const {
        return dst_iterator<ite_type>(edges.cbegin());
    }

    auto end() const {
        return dst_iterator<ite_type>(edges.cend());
    }
};

class dst_reverse_iteration {
    using ite_type = vec<Edge>::const_reverse_iterator;
    const vec<Edge> &edges;

public:
    dst_reverse_iteration(const vec<Edge> &edges) : edges(edges) { }

    auto begin() const {
        return dst_iterator<ite_type>(edges.crbegin());
    }

    auto end() const {
        return dst_iterator<ite_type>(edges.crend());
    }
};

dst_iteration dst(const vec<Edge> &edges) {
    return dst_iteration(edges);
}

dst_reverse_iteration rdst(const vec<Edge> &edges) {
    return dst_reverse_iteration(edges);
}

}

namespace tree {

struct LCA {
    using node_type = int;
   
    const size_type sz;
    const node_type root;

    template <typename Graph>
    LCA(const Graph &g, node_type root_arg)
        : sz(g.size()), root(root_arg), depth(sz), par(sz)
    {
        dfs(root, dummy, 0, g);
        std::fill(ALL(par[root]), dummy);
        for (int d = 0; d + 1 < log_sz; d++) for (int i = 0; i < sz; i++) {
            int p = par[i][d];
            par[i][d + 1] = (p == dummy ? dummy : par[p][d]);
        }
    }

    int get_depth(node_type i) const {
        return depth[i];
    }

    node_type operator()(node_type a, node_type b) const {
        if (depth[a] < depth[b]) std::swap(a, b);
        a = get_parent(a, depth[a] - depth[b]);
        if (a == b) return a;
        for (int d = log_sz - 1; 0 <= d; d--) {
            auto p1 = get_parent(a, d), p2 = get_parent(b, d);
            if (p1 != p2) {
                a = p1;
                b = p2;
            }
        }
        return par[a][0];
    }

private:
    static constexpr size_type log_sz = 30;
    static constexpr node_type dummy = -1;
    vec<int> depth;
    vec<std::array<node_type, log_sz>> par;

    node_type get_parent(node_type a, int d) const {
        for (int i = 0; d; i++, d /= 2) {
            if (a == dummy) return dummy;
            if (d & 1) a = par[a][i];
        }
        return a;
    }

    template <typename Graph>
    void dfs(node_type cur, node_type pre, ll d, const Graph &g) {
        par[cur][0] = pre;
        depth[cur] = d;
        for (auto nxt : graph::dst(g[cur])) {
            if (nxt == pre) continue;
            dfs(nxt, cur, d + 1, g);
        }
    }
};

}

struct Solver {
    ll n, q, c;
    graph::Graph<false> tree;
    vec<ll> xv;
    vvec<ll> dists, dp;
    const ll inf = 5e15;

    Solver(ll n, ll q, ll c)
        : n(n), q(q), c(c), tree(n), xv(q), 
          dists(std::move(make_v<ll>(n, n))), dp(std::move(make_v<ll>(q, n)))
    {
        for (ll i = 1; i < n; i++) {
            ll u, v, l;
            std::cin >> u >> v >> l;
            tree.add_edge(u - 1, v - 1, l);
        }
        for (ll &e : xv) {
            std::cin >> e;
            e--;
        }

        fill_seq(dp, [&](ll i, ll j) { return (i == 0 && j == xv[0]) ? 0 : inf; });
        calc_dists();
    }

    void calc_dists() {
        fill_seq(dists, [&](ll i, ll j) { return i == j ? 0 : -1; });
        
        {
            vec<pll> path = { pll(0, 0) };
            dfs(0, path, 0);
        }

        tree::LCA lca(tree, 0);
        for (ll i = 0; i < n; i++) for (ll j = i + 1; j < n; j++) {
            if (dists[i][j] != -1) continue;
            ll p = lca(i, j);
            dists[i][j] = dists[j][i] = dists[p][i] + dists[p][j];
        }
    }

    void dfs(ll cur, vec<pll> &path, ll sum) {
        for (auto [ p, d ] : path) dists[cur][p] = dists[p][cur] = sum + d;
        auto pre = path.back().first;
        path.emplace_back(cur, -sum);
        for (auto [ nxt, cost ] : tree[cur]) {
            if (nxt == pre) continue;
            dfs(nxt, path, sum + cost);
        }
        path.pop_back();
    }

    void update(ll idx) {
        const ll src = xv[idx], dst = xv[idx + 1];
        graph::Graph<true> g(n + 1);

        for (ll i = 0; i < n; i++) {
            g.add_edge(n, i, dp[idx][i] + std::min(c, dists[src][i]));
            for (auto [ j, c ] : tree[i]) {
                g.add_edge(i, j, c);
                g.add_edge(j, i, c);
            }
        }

        vec<ll> dv(n + 1, inf);
        dv[n] = 0;
        std::priority_queue<pll, vec<pll>, std::greater<pll>> pq;
        pq.emplace(0, n);
        while (pq.size()) {
            auto [ d, cur ] = pq.top();
            pq.pop();
            if (dv[cur] < d) continue;
            for (auto [ nxt, cost ] : g[cur]) {
                ll nd = d + cost;
                if (dv[nxt] <= nd) continue;
                dv[nxt] = nd;
                pq.emplace(nd, nxt);
            }
        }

        // don't jump
        for (ll i = 0; i < n; i++) {
            chmin(dp[idx + 1][i], dp[idx][i] + dists[src][dst]);
        }

        // jump
        for (ll i = 0; i < n; i++) {
            chmin(dp[idx + 1][i], dv[i] + dists[i][dst]);
        }
    }

    ll solve() {
        for (ll i = 0; i + 1 < q; i++) update(i);
        return *std::min_element(ALL(dp[q - 1]));
    }
};

int main() {
    ll n, q, c;
    std::cin >> n >> q >> c;
    Solver solver(n, q, c);
    std::cout << solver.solve() << "\n";
    return 0;
}