// >>> TEMPLATES
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using i32 = int32_t;
using i64 = int64_t;
using u32 = uint32_t;
using u64 = uint64_t;
#define int ll
#define rep(i,n) for (int i = 0; i < (int)(n); i++)
#define rep1(i,n) for (int i = 1; i <= (int)(n); i++)
#define repR(i,n) for (int i = (int)(n)-1; i >= 0; i--)
#define rep1R(i,n) for (int i = (int)(n); i >= 1; i--)
#define loop(i,a,B) for (int i = a; i B; i++)
#define loopR(i,a,B) for (int i = a; i B; i--)
#define all(x) begin(x), end(x)
#define allR(x) rbegin(x), rend(x)
#define rng(x,l,r) begin(x) + (l), begin(x) + (r)
#define pb push_back
#define eb emplace_back
#define fst first
#define snd second
template <class A, class B> auto mp(A &&a, B &&b) { return make_pair(forward<A>(a), forward<B>(b)); }
template <class... T> auto mt(T&&... x) { return make_tuple(forward<T>(x)...); }
template <class Int> auto constexpr inf = numeric_limits<Int>::max()/2-1;
auto constexpr INF32 = inf<int32_t>;
auto constexpr INF64 = inf<int64_t>;
auto constexpr INF   = inf<int>;
#ifdef LOCAL
#include "debug.hpp"
#else
#define dump(...) (void)(0)
#define say(x) (void)(0)
#define debug if (0)
#endif
template <class T, class Comp> struct pque : priority_queue<T, vector<T>, Comp> {
    vector<T> &data() { return this->c; }
    void clear() { this->c.clear(); }
};
template <class T> using pque_max = pque<T, less<T>>;
template <class T> using pque_min = pque<T, greater<T>>;
template <class T, class = typename T::iterator, enable_if_t<!is_same<T, string>::value, int> = 0>
ostream& operator<<(ostream& os, T const& a) { bool f = true; for (auto const& x : a) os << (f ? "" : " ") << x, f = false; return os; }
template <class T, size_t N, enable_if_t<!is_same<T, char>::value, int> = 0>
ostream& operator<<(ostream& os, const T (&a)[N]) { bool f = true; for (auto const& x : a) os << (f ? "" : " ") << x, f = false; return os; }
template <class T, class = decltype(begin(declval<T&>())), class = typename enable_if<!is_same<T, string>::value>::type>
istream& operator>>(istream& is, T &a) { for (auto& x : a) is >> x; return is; }
template <class T, class S> ostream& operator<<(ostream& os, pair<T,S> const& p) { return os << p.first << " " << p.second; }
template <class T, class S> istream& operator>>(istream& is, pair<T,S>& p) { return is >> p.first >> p.second; }
struct IOSetup { IOSetup() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); } } iosetup;
template <class F> struct FixPoint : private F {
    constexpr FixPoint(F&& f) : F(forward<F>(f)) {}
    template <class... T> constexpr auto operator()(T&&... x) const { return F::operator()(*this, forward<T>(x)...); }
};
struct MakeFixPoint { template <class F> constexpr auto operator|(F&& f) const { return FixPoint<F>(forward<F>(f)); } };
#define MFP MakeFixPoint()|
#define def(name, ...) auto name = MFP [&](auto &&name, __VA_ARGS__)
template <class T, size_t d> struct vec_impl {
    using type = vector<typename vec_impl<T,d-1>::type>;
    template <class... U> static type make_v(size_t n, U&&... x) { return type(n, vec_impl<T,d-1>::make_v(forward<U>(x)...)); }
};
template <class T> struct vec_impl<T,0> { using type = T; static type make_v(T const& x = {}) { return x; } };
template <class T, size_t d = 1> using vec = typename vec_impl<T,d>::type;
template <class T, size_t d = 1, class... Args> auto make_v(Args&&... args) { return vec_impl<T,d>::make_v(forward<Args>(args)...); }
template <class T> void quit(T const& x) { cout << x << endl; exit(0); }
template <class T, class U> constexpr bool chmin(T& x, U const& y) { if (x > y) { x = y; return true; } return false; }
template <class T, class U> constexpr bool chmax(T& x, U const& y) { if (x < y) { x = y; return true; } return false; }
template <class It> constexpr auto sumof(It b, It e) { return accumulate(b, e, typename iterator_traits<It>::value_type{}); }
template <class T> int sz(T const& x) { return x.size(); }
template <class C, class T> int lbd(C const& v, T const& x) { return lower_bound(begin(v), end(v), x)-begin(v); }
template <class C, class T> int ubd(C const& v, T const& x) { return upper_bound(begin(v), end(v), x)-begin(v); }
const int dx[] = { 1,0,-1,0,1,-1,-1,1 };
const int dy[] = { 0,1,0,-1,1,1,-1,-1 };
constexpr int popcnt(ll x) { return __builtin_popcountll(x); }
// [a,b]
template <class Int> Int rand(Int a, Int b) { static mt19937_64 mt{random_device{}()}; return uniform_int_distribution<Int>(a,b)(mt); }
i64 irand(i64 a, i64 b) { return rand<i64>(a,b); }
u64 urand(u64 a, u64 b) { return rand<u64>(a,b); }
// <<<
// >>> LCA (RMQ)
#ifndef EDGE_INFO
#define EDGE_INFO
constexpr int dest(int v) { return v; }
template <class E, class = decltype(declval<E>().to)>
constexpr int dest(E const& e) { return e.to; }
constexpr int cost(int) { return 1; }
template <class E, class = decltype(declval<E>().cost)>
constexpr auto cost(E const& e) { return e.cost; }
template <class E> using cost_t = decltype(cost(declval<E>()));
#endif

template <class E, class RMQ> struct LCA {
    vector<vector<E>> const* g;
    int32_t n, root;
    vector<int32_t> id;
    vector<cost_t<E>> d;
    RMQ rmq;
    LCA() {}
    LCA(vector<vector<E>> const* g, int root)
        : g(g), n(g->size()), root(root), id(n), d(n) {
        vector<pair<int, int>> a;
        a.reserve(n-1);
        auto dfs = [&](auto dfs, int x, int p, int d0, cost_t<E> d1) -> void {
            id[x] = a.size();
            d[x] = d1;
            for (auto const& e : (*g)[x]) {
                if (dest(e) == p) continue;
                a.emplace_back(d0, x);
                dfs(dfs, dest(e), x, d0 + 1, d1 + cost(e));
            }
        };
        dfs(dfs, root, -1, 0, 0);
        rmq = RMQ(a);
    }
    cost_t<E> dep(int a) const { return d[a]; }
    int operator()(int a, int b) const { return lca(a,b); }
    int lca(int a, int b) const {
        if (a == b) return a;
        if (id[a] > id[b]) swap(a, b);
        return rmq.get(id[a], id[b]).second;
    }
    cost_t<E> dist(int a, int b) const { return d[a] + d[b] - 2*d[lca(a,b)]; }
};

namespace RMQ {
// >>> DST
template <class Handler>
struct DST : Handler {
    using Value = typename Handler::Value;
    using Handler::unit; // () -> Value
    using Handler::merge; // (Value, Value) -> Value
    static constexpr int bsr(int32_t x) { return x ? 31-__builtin_clz(x) : -1; }

    vector<vector<Value>> v;
    DST() {}
    template <class... T> DST(T&&... x) { build(forward<T>(x)...); }
    void build(int n) { build(n, unit()); }
    void build(int n, Value const& x) { build(n, [&](int) { return x; }); }
    void build(vector<Value> const& v) { build(v.size(), [&](int i) { return v[i]; }); }
    template <class F, class = decltype(declval<F>()(0))>
    void build(int n, F gen)  {
        assert(n >= 0);
        v.resize(1);
        v[0].resize(n, unit());
        for (int i = 0; i < n; i++) v[0][i] = gen(i);
        if (n <= 1) return;
        const int lg = __lg(2*n-1);
        v.resize(lg, vector<Value>(n, unit()));
        for (int h = 1; h < lg; ++h) {
            const int w = 1<<h;
            for (int b = w; b < n; b += (w<<1)) {
                Value x = unit();
                for (int j = b-1; j >= b-w; --j) {
                    v[h][j] = x = merge(v[0][j], x);
                }
                x = unit();
                for (int j = b; j < min(n,b+w); ++j) {
                    v[h][j] = x = merge(x, v[0][j]);
                }
            }
        }
    }
    int size() const { return v.empty() ? 0 : v[0].size(); }
    Value get(int l, int r) const {
        assert(0 <= l); assert(l <= r); assert(r <= size());
        if (l == r) return unit();
        --r;
        if (l == r) return v[0][l];
        const int h = bsr(l^r);
        return merge(v[h][l], v[h][r]);
    }
    Value operator[](int idx) const {
        assert(0 <= idx); assert(idx < size());
        return v[0][idx];
    }
};
// <<<
struct Min {
    using Value = pair<int, int>;
    static constexpr auto inf = numeric_limits<int>::max();
    constexpr static Value unit() { return { inf, inf }; }
    constexpr static Value merge(Value const& x, Value const& y) { return min(x, y); }
};
using RMQ = DST<Min>;
}

template <class E>
auto get_lca(vector<vector<E>> const& g, int root = 0) {
    return LCA<E, RMQ::RMQ>(&g, root);
}
// <<<

int32_t main() {
    int n, q, c; cin >> n >> q >> c;
    struct edge { int to, cost; };
    vector<vector<edge>> g(n);
    rep (i,n-1) {
        int a, b, c; cin >> a >> b >> c; --a, --b;
        g[a].pb({b, c});
        g[b].pb({a, c});
    }
    vector<int> x(q); cin >> x;
    for (auto &e : x) cin >> e, e--;

    auto lca = get_lca(g);

    vector<int> dp(n, INF);
    dp[x[0]] = 0;
    rep (i,q-1) {
        vector<int> ndp(n, INF), dep(n);

        def (dfs, int a, int p, int d) -> int {
            chmin(ndp[a], dp[a] + c + d);
            dep[a] = d;
            for (auto e : g[a]) {
                if (e.to == p) continue;
                chmin(ndp[a], dfs(e.to, a, d + e.cost));
            }
            return ndp[a];
        };
        dfs(x[i+1], -1, 0);

        int min_dp = *min_element(all(dp));
        int dist = lca.dist(x[i], x[i+1]);
        rep (j,n) {
            chmin(ndp[j], dp[j] + dist);
            chmin(ndp[j], min_dp + lca.dist(x[i], j) + lca.dist(j, x[i+1]));
        }

        swap(dp, ndp);
    }

    cout << *min_element(all(dp)) << endl;

}