#include <bits/stdc++.h>

using namespace std; const int maxn = 5e5 + 5; typedef long long ll;

int n, k, c[maxn];

struct edge { int v, w; }; vector<edge> T[maxn];

inline ll gcd(ll x, ll y)
{
    return !y ? x : gcd(y, x % y);
}

struct GCD
{
    ll x, y;

    bool hv;

    GCD operator +(const GCD &b) const
    {
        if (!hv) return b;
        else if (!b.hv) return *this;
        else
        {
            return { x, gcd(gcd(y, b.y), abs(b.x - x)), 1 };
        }
    }

    inline GCD add(int z) { return { x + z, y, hv }; }
};

int vl[maxn];

int S1[maxn]; ll S2[maxn];

GCD G[maxn];

void dp0(int u, int fa)
{
    S1[u] = vl[u];
    if (vl[u]) G[u].hv = 1;
    for (auto e : T[u]) if (e.v != fa)
    {
        dp0(e.v, u);
        S1[u] += S1[e.v];
        S2[u] += S2[e.v] + S1[e.v] * e.w;
        G[u] = G[u] + G[e.v].add(e.w);
    }
}

GCD H[maxn]; ll S[maxn];

void dp1(int u, int fa)
{
    // cerr << u << ' ' << H[u].x << ' ' << H[u].y << ' ' << H[u].hv << ' ' << G[u].x << ' ' << G[u].y << ' ' << G[u].hv << endl;
    GCD t = { 0, 0, 0 };
    for (auto e : T[u]) if (e.v != fa)
    {
        H[e.v] = H[e.v] + t.add(e.w);
        t = t + G[e.v].add(e.w);
    }
    reverse(T[u].begin(), T[u].end()), t = { 0, 0, 0 };
    for (auto e : T[u]) if (e.v != fa)
    {
        H[e.v] = H[e.v] + t.add(e.w);
        t = t + G[e.v].add(e.w);
    }
    GCD add = { 0, 0, 0 }; if (vl[u]) add.hv = 1; add = add + H[u];
    for (auto e : T[u]) if (e.v != fa)
    {
        H[e.v] = H[e.v] + add.add(e.w);
        S[e.v] = S[u] + ll(k - 2 * S1[e.v]) * e.w;
        dp1(e.v, u);
    }
}

int main()
{
    scanf("%d%d", &n, &k);
    for (int i = 1; i <= k; i++) scanf("%d", c + i);
    for (int i = 1, u, v, w; i < n; i++) scanf("%d%d%d", &u, &v, &w), T[u].push_back({ v, w }), T[v].push_back({ u, w });
    for (int i = 1; i <= k; i++) vl[c[i]]++;
    dp0(1, 0), S[1] = S2[1], dp1(1, 0);
    ll ans = 1e18;
    for (int i = 1; i <= n; i++)
    {
        G[i] = G[i] + H[i];
        // cerr << i << ' ' << S[i] << ' ' << abs(gcd(G[i].x, G[i].y)) << endl;
        ans = min(ans, S[i] / abs(gcd(G[i].x, G[i].y)));
    }
    return 0 * printf("%lld\n", ans * 2);
}