#include <bits/stdc++.h>
using namespace std;
using ll = long long;
template <class t, class u>
void chmax(t& first, u second) {
  if (first < second) first = second;
}
template <class t, class u>
void chmin(t& first, u second) {
  if (second < first) first = second;
}
template <class t>
using vc = vector<t>;
template <class t>
using vvc = vc<vc<t>>;
using pi = pair<ll, ll>;
using vi = vc<ll>;
template <class t, class u>
ostream& operator<<(ostream& os, const pair<t, u>& p) {
  return os << "{" << p.first << "," << p.second << "}";
}
template <class t>
ostream& operator<<(ostream& os, const vc<t>& v) {
  os << "{";
  for (auto e : v) os << e << ",";
  return os << "}";
}
using uint = unsigned;
using ull = unsigned long long;
template <ll i, class T>
void print_tuple(ostream&, const T&) {}
template <ll i, class T, class H, class... Args>
void print_tuple(ostream& os, const T& t) {
  if (i) os << ",";
  os << get<i>(t);
  print_tuple<i + 1, T, Args...>(os, t);
}
template <class... Args>
ostream& operator<<(ostream& os, const tuple<Args...>& t) {
  os << "{";
  print_tuple<0, tuple<Args...>, Args...>(os, t);
  return os << "}";
}
void print(ll x, ll suc = 1) {
  cout << x;
  if (suc == 1) cout << "\n";
  if (suc == 2) cout << " ";
}
ll read() {
  ll i;
  cin >> i;
  return i;
}
vi readvi(ll n, ll off = 0) {
  vi v(n);
  for (ll i = ll(0); i < ll(n); i++) v[i] = read() + off;
  return v;
}
template <class T>
void print(const vector<T>& v, ll suc = 1) {
  for (ll i = ll(0); i < ll(v.size()); i++)
    print(v[i], i == ll(v.size()) - 1 ? suc : 2);
}
string readString() {
  string s;
  cin >> s;
  return s;
}
template <class T>
T sq(const T& t) {
  return t * t;
}
void yes(bool ex = true) {
  cout << "Yes" << endl;
  if (ex) exit(0);
}
void no(bool ex = true) {
  cout << "No" << endl;
  if (ex) exit(0);
}
constexpr ll ten(ll n) { return n == 0 ? 1 : ten(n - 1) * 10; }
const ll infLL = LLONG_MAX / 3;
const ll inf = infLL;
ll topbit(signed t) { return t == 0 ? -1 : 31 - __builtin_clz(t); }
ll topbit(ll t) { return t == 0 ? -1 : 63 - __builtin_clzll(t); }
ll botbit(signed first) { return first == 0 ? 32 : __builtin_ctz(first); }
ll botbit(ll first) { return first == 0 ? 64 : __builtin_ctzll(first); }
ll popcount(signed t) { return __builtin_popcount(t); }
ll popcount(ll t) { return __builtin_popcountll(t); }
bool ispow2(ll i) { return i && (i & -i) == i; }
ll mask(ll i) { return (ll(1) << i) - 1; }
bool inc(ll first, ll second, ll c) { return first <= second && second <= c; }
template <class t>
void mkuni(vc<t>& v) {
  sort(v.begin(), v.end());
  v.erase(unique(v.begin(), v.end()), v.end());
}
ll rand_int(ll l, ll r) {
  static random_device rd;
  static mt19937_64 gen(rd());
  return uniform_int_distribution<ll>(l, r)(gen);
}
template <class t>
ll lwb(const vc<t>& v, const t& first) {
  return lower_bound(v.begin(), v.end(), first) - v.begin();
}
template <class N, class E>
struct treedp {
  const vvc<E>& g;
  vvc<N> dp1, dp2;
  vc<N> res;
  N dfs1(ll v, ll p) {
    N tmp;
    tmp.init(v);
    dp1[v].push_back(tmp);
    E up;
    for (auto e : g[v])
      if (e != p)
        dp1[v].push_back(dfs1(e, v));
      else
        up = e;
    dp2[v] = dp1[v];
    for (ll i = ll(1); i < ll(dp2[v].size()); i++)
      dp2[v][i] = dp2[v][i - 1] + dp2[v][i];
    if (p == -1)
      return N();
    else
      return dp2[v].back().up(up);
  }
  void dfs2(ll v, ll p, N cur) {
    res[v] = cur + dp2[v].back();
    for (ll i = ll(g[v].size()) - 1; i >= ll(0); i--) {
      auto e = g[v][i];
      if (e == p) continue;
      dp2[v].pop_back();
      dfs2(e, v, (cur + dp2[v].back()).up(e));
      cur = cur + dp1[v].back();
      dp1[v].pop_back();
    }
  }
  treedp(const vvc<E>& gg)
      : g(gg), dp1(g.size()), dp2(g.size()), res(g.size()) {
    dfs1(0, -1);
    N tmp;
    tmp.init(0);
    dfs2(0, -1, tmp);
  }
};
vi ok;
struct N {
  bool rok;
  ll x, y;
  void init(ll vv) {
    rok = ok[vv];
    x = 0;
    y = -1;
  }
  N up(ll to) const {
    N res;
    res.init(to);
    if (res.rok) {
      if (rok) {
        if (y == -1) {
          res.x = x + 1;
        } else {
          res.y = x + y + 1;
        }
      } else {
        res.y = 0;
      }
    }
    return res;
  }
  N operator+(const N& r) const {
    if (!rok) return *this;
    N res;
    res.rok = 1;
    res.x = x + r.x;
    res.y = max(y, r.y);
    return res;
  }
  ll getans() {
    if (rok)
      return 1 + x + y;
    else
      return 0;
  }
};
signed main() {
  cin.tie(0);
  ios::sync_with_stdio(0);
  cout << fixed << setprecision(20);
  ll n, k;
  cin >> n >> k;
  vvc<ll> g(n);
  vi val = readvi(n);
  for (ll i = ll(0); i < ll(n - 1); i++) {
    ll first, second;
    cin >> first >> second;
    first--;
    second--;
    g[first].push_back(second);
    g[second].push_back(first);
  }
  vi vs = val;
  mkuni(vs);
  ll lw = 0, up = vs.size();
  while (up - lw > 1) {
    const ll mid = (lw + up) / 2;
    ok.resize(n);
    for (ll i = ll(0); i < ll(n); i++) ok[i] = val[i] >= vs[mid];
    auto dp = treedp<N, ll>(g).res;
    bool can = 0;
    for (ll i = ll(0); i < ll(n); i++)
      if (dp[i].getans() >= k) can = 1;
    if (can)
      lw = mid;
    else
      up = mid;
  }
  cout << vs[lw] << endl;
}
