#include <bits/stdc++.h>
using namespace std;
template <typename T>
bool readInteger(T& x) {
  char c, r = 0, n = 0;
  x = 0;
  for (;;) {
    c = getchar();
    if ((c < 0) && (!r))
      return (0);
    else if ((c == '-') && (!r))
      n = 1;
    else if ((c >= '0') && (c <= '9'))
      x = x * 10 + c - '0', r = 1;
    else if (r)
      break;
  }
  if (n) x = -x;
  return (1);
}
template <typename T, T MOD>
struct ModInt {
  T value;
  ModInt() : value(0) {}
  ModInt(T x) {
    x %= MOD;
    if (x < 0) x += MOD;
    value = x;
  }

 private:
  T __________________(T ___, T ____) {
    if (!____) return ___;
    return __________________(____, ___ % ____);
  }
  T _____________(T _, T __, T ____, T ___) {
    T _____, ______, _______ = ____ - _;
    assert(!(_______ % __________________(__, ___)));
    for (_____ = ______ = 0; _____ - ______ != _______;) {
      _____ = (_______ + ______ + __ - 1) / __ * __;
      ______ = (_____ - _______ + ___ - 1) / ___ * ___;
    }
    return _____ + _;
  }

 public:
  ModInt& operator+=(ModInt x) {
    value += x.value;
    if (value >= MOD) value -= MOD;
    return *this;
  }
  ModInt& operator-=(ModInt x) {
    value -= x.value;
    if (value < 0) value += MOD;
    return *this;
  }
  ModInt& operator*=(ModInt x) {
    value *= x.value;
    value %= MOD;
    return *this;
  }
  ModInt& operator/=(ModInt x) {
    x.invert();
    return *this *= x;
  }
  ModInt operator+(ModInt x) const {
    ModInt o = *this;
    o += x;
    return o;
  }
  ModInt operator-(ModInt x) const {
    ModInt o = *this;
    o -= x;
    return o;
  }
  ModInt operator*(ModInt x) const {
    ModInt o = *this;
    o *= x;
    return o;
  }
  ModInt operator/(ModInt x) const {
    ModInt o = *this;
    o /= x;
    return o;
  }
  bool operator==(ModInt x) const { return value == x.value; }
  bool operator!=(ModInt x) const { return !(*this == x); }
  ModInt operator-() const { return ModInt(0) - *this; }
  ModInt operator^(long long x) const {
    ModInt ret = 1;
    ModInt mul = *this;
    while (x) {
      if (x & 1) ret *= mul;
      mul *= mul;
      x >>= 1;
    }
    return ret;
  }
  ModInt& operator^=(long long x) { return *this = *this ^ x; }

 private:
  void invert() { *this ^= MOD - 2; }

 public:
  void answer() { std::cout << value << std::endl; }
};
const int MX = 2.1e5;
int N, K;
int ai[MX];
vector<int> E[MX];
vector<int> child[MX];
bool light[MX];
long long dp[MX][5];
const int NINF = -1e9;
void solve(int x) {
  for (auto& o : (child[x])) solve(o);
  long long useNow = NINF;
  {
    long long& ans = dp[x][4];
    ans = NINF;
    if (light[x]) {
      {
        long long sum = 1;
        long long bestDelta = 0;
        for (auto& o : (child[x])) {
          sum += dp[o][3];
          bestDelta = max(bestDelta, dp[o][4] - dp[o][3]);
        }
        sum += bestDelta;
        ans = max(ans, sum);
      }
      {
        long long sum = 1;
        long long bestA = 0;
        long long bestB = 0;
        for (auto& o : (child[x])) {
          long long v1 = max(0LL, dp[o][3]);
          long long v2 = dp[o][2];
          sum += v1;
          long long delta = v2 - v1;
          if (delta > bestA) {
            bestB = bestA;
            bestA = delta;
          } else
            bestB = max(bestB, delta);
        }
        useNow = sum + bestA + bestB;
        ans = max(ans, useNow);
      }
    }
  }
  {
    long long& ans = dp[x][3];
    ans = NINF;
    if (light[x]) {
      long long sum = 1;
      for (auto& o : (child[x])) sum += dp[o][3];
      ans = max(ans, sum);
    }
  }
  {
    long long& ans = dp[x][2];
    ans = NINF;
    if (light[x]) {
      long long sum = 1;
      long long bestDelta = 0;
      for (auto& o : (child[x])) {
        long long v1 = max(0LL, dp[o][3]);
        long long v2 = dp[o][2];
        sum += v1;
        bestDelta = max(bestDelta, v2 - v1);
      }
      sum += bestDelta;
      ans = max(ans, sum);
    }
  }
  {
    long long& ans = dp[x][1];
    ans = useNow;
    for (auto& o : (child[x])) ans = max(ans, dp[o][1]);
  }
}
int ROOT = 0;
bool ok(int threshold) {
  for (int i = (0); i < int(N); i++) light[i] = ai[i] >= threshold;
  if (light[ROOT]) return true;
  solve(ROOT);
  return dp[ROOT][1] >= K;
}
void init(int x, int par) {
  for (auto& o : (E[x]))
    if (o != par) {
      child[x].push_back(o);
      init(o, x);
    }
}
int main() {
  readInteger(N);
  readInteger(K);
  for (int i = (0); i < int(N); i++) readInteger(ai[i]);
  for (int k = (0); k < int(N - 1); k++) {
    int u, v;
    readInteger(u);
    readInteger(v);
    --u, --v;
    E[u].push_back(v);
    E[v].push_back(u);
  }
  for (int i = (0); i < int(N); i++)
    if (ai[i] < ai[ROOT]) ROOT = i;
  init(ROOT, -1);
  vector<int> vals(N);
  for (int i = (0); i < int(N); i++) vals[i] = ai[i];
  sort(vals.begin(), vals.end());
  reverse(vals.begin(), vals.end());
  int lo = K - 1;
  int hi = N - 1;
  while (lo != hi) {
    int mid = (lo + hi) / 2;
    if (ok(vals[mid]))
      hi = mid;
    else
      lo = mid + 1;
  }
  printf("%d\n", vals[lo]);
}
