#include<iostream>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<bitset>
#include<stack>
#include<unordered_map>
#include<utility>
#include<cassert>
#include<complex>
#include<numeric>
#include<array>
using namespace std;

//#define int long long
typedef long long ll;

typedef unsigned long long ul;
typedef unsigned int ui;
constexpr ll mod = 1000000007;
const ll INF = mod * mod;
typedef pair<int, int>P;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
#define all(v) (v).begin(),(v).end()
typedef pair<ll, ll> LP;
typedef long double ld;
typedef pair<ld, ld> LDP;
const ld eps = 1e-12;
const ld pi = acosl(-1.0);

ll mod_pow(ll x, ll n, ll m = mod) {
	ll res = 1;
	while (n) {
		if (n & 1)res = res * x % m;
		x = x * x % m; n >>= 1;
	}
	return res;
}
struct modint {
	ll n;
	modint() :n(0) { ; }
	modint(ll m) :n(m) {
		if (n >= mod)n %= mod;
		else if (n < 0)n = (n % mod + mod) % mod;
	}
	operator int() { return n; }
};
bool operator==(modint a, modint b) { return a.n == b.n; }
modint operator+=(modint& a, modint b) { a.n += b.n; if (a.n >= mod)a.n -= mod; return a; }
modint operator-=(modint& a, modint b) { a.n -= b.n; if (a.n < 0)a.n += mod; return a; }
modint operator*=(modint& a, modint b) { a.n = ((ll)a.n * b.n) % mod; return a; }
modint operator+(modint a, modint b) { return a += b; }
modint operator-(modint a, modint b) { return a -= b; }
modint operator*(modint a, modint b) { return a *= b; }
modint operator^(modint a, ll n) {
	if (n == 0)return modint(1);
	modint res = (a * a) ^ (n / 2);
	if (n % 2)res = res * a;
	return res;
}

ll inv(ll a, ll p) {
	return (a == 1 ? 1 : (1 - p * inv(p % a, a)) / a + p);
}
modint operator/(modint a, modint b) { return a * modint(inv(b, mod)); }

const int max_n = 1000;
modint fact[max_n], factinv[max_n];
void init_f() {
	fact[0] = modint(1);
	for (int i = 0; i < max_n - 1; i++) {
		fact[i + 1] = fact[i] * modint(i + 1);
	}
	factinv[max_n - 1] = modint(1) / fact[max_n - 1];
	for (int i = max_n - 2; i >= 0; i--) {
		factinv[i] = factinv[i + 1] * modint(i + 1);
	}
}
modint comb(int a, int b) {
	if (a < 0 || b < 0 || a < b)return 0;
	return fact[a] * factinv[b] * factinv[a - b];
}

int gcd(int a, int b) {
	if (a < b)swap(a, b);
	while (b) {
		int r = a % b; a = b; b = r;
	}
	return a;
}
struct lcagraph {
private:
	int n;
	vector<vector<int>> G;
	vector<vector<int>> parent;
	vector<int> depth;
	int root;
	int tmp;
public:
	lcagraph(int n_) {
		n = n_;
		G.resize(n);
		parent.resize(n);
		depth.resize(n);
		tmp = 0;
		int cop = n;
		while (cop) {
			tmp++; cop /= 2;
		}
		rep(i, n)parent[i].resize(tmp);
		root = 0;
	}
	lcagraph() {}
	void init(int n_) {
		n = n_;
		G.resize(n);
		parent.resize(n);
		depth.resize(n);
		tmp = 0;
		int cop = n;
		while (cop) {
			tmp++; cop /= 2;
		}
		rep(i, n)parent[i].resize(tmp);
		root = 0;
	}
	void add_edge(int a, int b) {
		G[a].push_back(b);
		G[b].push_back(a);
	}
	void dfs(int id, int fr, int d) {
		parent[id][0] = fr;
		depth[id] = d;
		rep(j, G[id].size()) {
			int to = G[id][j];
			if (to == fr)continue;
			dfs(to, id, d + 1);
		}
	}
	void complete(int r = 0) {
		root = r;
		dfs(root, -1, 0);
		rep(j, tmp - 1)rep(i, n) {
			if (parent[i][j] < 0)parent[i][j + 1] = -1;
			else parent[i][j + 1] = parent[parent[i][j]][j];
		}
	}
	int lca(int u, int v) {
		if (depth[u] > depth[v])swap(u, v);
		for (int k = 0; k < tmp; k++) {
			if ((depth[v] - depth[u]) >> k & 1) {
				v = parent[v][k];
			}
		}
		if (u == v)return u;
		for (int k = tmp - 1; k >= 0; k--) {
			if (parent[u][k] != parent[v][k]) {
				u = parent[u][k];
				v = parent[v][k];
			}
		}
		return parent[u][0];
	}
	int dep(int x) {
		return depth[x];
	}
	int dist(int x, int y) {
		int l = lca(x, y);
		return depth[x] + depth[y] - 2 * depth[l];
	}
};



struct BIT {
private:
	vector<ll> node; int n;
public:
	BIT(int n_) {
		n = n_; node.resize(n, 0);
	}
	//0-indexed
	void add(int a, ll w) {
		for (int i = a; i < n; i |= i + 1)node[i] += w;
	}
	//[0,a)
	ll sum(int a) {
		ll ret = 0;
		for (int i = a - 1; i >= 0; i = (i & (i + 1)) - 1)ret += node[i];
		return ret;
	}
	//[a,b)
	ll sum(int a, int b) {
		return sum(b) - sum(a);
	}
};
void solve() {
	int n, k; cin >> n >> k;
	vector<vector<int>> G(n);
	vector<int> c(k); rep(i, k) {
		cin >> c[i]; c[i]--;
	}
	vector<ll> d(k); rep(i, k)cin >> d[i];
	lcagraph lg(n);
	rep(i, n - 1) {
		int a, b; cin >> a >> b; a--; b--;
		G[a].push_back(b); G[b].push_back(a);
		lg.add_edge(a, b);
	}
	lg.complete();
	vector<int> le(k + 1);
	vector<ll> lesum(k + 1);
	le[1] = c[1]; lesum[1] = d[1];
	for (int i = 2; i <= k; i++) {
		le[i] = lg.lca(le[i - 1], c[i-1]);
		lesum[i] = lesum[i - 1] + d[i-1];
	}
	vector<int> ri(k + 1);
	vector<ll> risum(k + 1);
	ri[1] = c.back(); risum[1] = d.back();
	for (int i = 2; i <= k; i++) {
		ri[i] = lg.lca(ri[i - 1], c[k - i]);
		risum[i] = risum[i - 1] + d[k - i];
	}
	vector<ll> vx;
	rep1(i, k)vx.push_back(lesum[i]);
	rep1(i, k)vx.push_back(risum[i]);
	sort(all(vx));
	vx.erase(unique(all(vx)), vx.end());
	rep1(i, k) {
		lesum[i] = lower_bound(all(vx), lesum[i]) - vx.begin();
		risum[i] = lower_bound(all(vx), risum[i]) - vx.begin();
	}
	vector<pair<LP, int>> vs;
	rep1(i, k - 1) {
		int d = lg.dep(lg.lca(le[i], c.back()));
		vs.push_back({ {d,lesum[i]},0 });
		d = lg.dep(lg.lca(c[0], ri[i]));
		vs.push_back({ {d,risum[i] }, 1});
	}
	sort(all(vs));
	
	auto calc = [&](ll x)->ll {
		ll res = 0;
		rep1(i, k - 1) {
			ll val = vx[lesum[i]] + lg.dep(le[i]);
			if (val <= x)res++;
			val = vx[risum[i]] + lg.dep(ri[i]);
			if (val <= x)res++;
		}
	
		BIT btle(vx.size()), btri(vx.size());
		for (pair<LP, int> p : vs) {
			ll r = x - vx[p.first.second] - p.first.first;
			int id = upper_bound(all(vx), r) - vx.begin();
			if (p.second) {
				res += btle.sum(0, id);
				btri.add(p.first.second, 1);
			}
			else {
				res += btri.sum(0, id);
				btle.add(p.first.second, 1);
			}
		}
		BIT bt(vx.size());
		int ad = lg.dep(le[k]);
		rep1(i, k - 1) {
			//add k-1-i
			bt.add(risum[k - 1 - i], 1);
			ll r = x - vx[lesum[i]] - ad;
			int id = upper_bound(all(vx), r) - vx.begin();
			res -= bt.sum(0, id);
		}
		return res;
	};
	ll alnum = (ll)k * (k - 1) / 2;
	ll l = -1000000000000000;
	ll r = -l;
	while (r - l > 1) {
		ll mid = (l + r) / 2;
		ll num = calc(mid);
		//cout << mid << " " << num << "\n";
		if (num * 2 >= alnum) {
			r = mid;
		}
		else {
			l = mid;
		}
	}
	cout << l << "\n";
}

signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	//cout << fixed << setprecision(15);
	//init_f(); 
	//init();
	//expr();
	//int t; cin >> t; rep(i, t)
	solve();
	return 0;
}