#include <bits/stdc++.h>
using namespace std;
#define int long long
#define endl '\n'
const int N = 5e5 + 5,INF = 1e18;
#define ls (u << 1)
#define rs (u << 1 | 1)
#define sum(u) (tr[u].sum)
#define d(u) (tr[u].d)
#define tot(u) (tr[u].tot)
struct node{
	int l,r;
	int sum,d;
	int tot;
}tr[N << 2];
int a[N],b[N];

void pushup(int u)
{
	sum(u) = sum(ls) + sum(rs);tot(u) = tot(ls) + tot(rs);
	d(u) = __gcd(d(ls), d(rs));
}

void build(int u,int l,int r)
{
	if(l == r)tr[u] = {l, l, a[l], a[l], b[l]};
	else 
	{
		tr[u] = {l, r};
		int mid = l + r >> 1;
		build(ls, l, mid);
		build(rs, mid + 1, r);
		pushup(u);
	}
}

void upd(int u,int x,int d)
{
	if(tr[u].l == tr[u].r)
	{
		sum(u) = x;
		d(u) = x;tot(u) = x;
	}
	else 
	{
		int mid = tr[u].l + tr[u].r >> 1;
		if(x <= mid)upd(ls, x, d);
		else upd(rs, x, d);
		pushup(u);
	}
}

node que(int u,int l,int r)
{
	if(tr[u].l >= l && tr[u].r <= r)
	{
		return tr[u];
	}
	else 
	{
		int mid = tr[u].l + tr[u].r >> 1;
		node res = {0,0,0,0};
		if(l <= mid)
		{
			res = que(ls, l, r);
		}
		if(r > mid)
		{
			node tmp = que(rs ,l ,r);
			res.sum += tmp.sum;
			res.d = __gcd(res.d, tmp.d);
		}
		return res;
	}
}
int quesum(int l,int r)
{
	return que(1, l, r).sum;
}
int quegcd(int l,int r)
{
	int sum = 0;
	sum = que(1, 1, l).sum;
	int d = 0;
	if(l != r)
 	d = que(1, l + 1, r).d;
	return abs(__gcd(sum, d));
}
bool st[N];vector<pair<int,int>> g[N];
int cnt,dfsn[N],rdfsn[N],n,k;
void dfs(int u,int f,int d)
{
	dfsn[u] = INF;
	if(st[u])dfsn[u] = ++cnt,rdfsn[u] = cnt,b[dfsn[u]] = d;
	for(auto t : g[u])
	{
		int to = t.first,val = t.second;
		if(to == f)continue;
		dfs(to, u, d + val);
		dfsn[u] = min(dfsn[u], dfsn[to]);
		rdfsn[u] = max(rdfsn[to], rdfsn[u]);
	}	
}

void upd1(int l,int r,int x)
{
	if(l < 1 || r > k || l > r)return;
	upd(1, l, x);
	if(r + 1 <= k)upd(1, r + 1, -x);	
}

int ans = 1e18;
void dfs1(int u,int f)
{
	int res = quegcd(1,k);
	int dis = tr[1].tot;
	ans = min(ans, dis / res);
	for(auto t : g[u])
	{
		int to = t.first,val = t.second;
		if(to == f)continue;
		int l = dfsn[to],r = rdfsn[to];
		if(l <= r)
		{
			upd1(l, r, -val);
			upd1(1, l, val);
			upd1(r + 1, k, val);
			dfs1(to, u);
			upd1(l, r, val);
			upd1(1, l, -val);
			upd1(r + 1, k, -val);
		}
		else
		{
			upd1(1, k, val);
			dfs1(to, u);
			upd1(1, k, -val);
		}
	}
}

signed main()
{
	cin >> n >> k;
	for(int i = 1;i <= k;i++)
	{
		int t;cin >> t;st[t] = true;
	}
	for(int i = 1;i < n;i++)
	{
		int u,v,w;cin >> u >> v >> w;
		g[u].push_back({v,w});
		g[v].push_back({u,w});
	}
	dfs(1,0,0);
	for(int i = 1;i <= k;i++)a[i] = b[i] - b[i - 1];
	build(1,1,k);
	dfs1(1,0);
	cout << ans * 2 << endl;
}