#include <bits/stdc++.h>
using namespace std;
int n, m, mid, rt, res, a[200010], f[200010], sz[200010];
vector<int> e[200010];
void dfs(int u, int fa) {
  f[u] = sz[u] = 1;
  int m1 = 0, m2 = 0;
  for (auto v : e[u]) {
    if (v == fa) continue;
    dfs(v, u);
    sz[u] += sz[v];
    if (f[v] == sz[v])
      f[u] += f[v];
    else {
      if (f[v] > m1) swap(f[v], m1);
      if (f[v] > m2) swap(f[v], m2);
    }
  }
  f[u] = a[u] < mid ? 0 : f[u] + m1;
  res = max(res, f[u] + m2);
}
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; i++) scanf("%d", &a[i]);
  for (int i = 1; i < n; i++) {
    int u, v;
    scanf("%d%d", &u, &v);
    e[u].push_back(v);
    e[v].push_back(u);
  }
  rt = min_element(a + 1, a + 1 + n) - a;
  int l = 0, r = 1000010, ans;
  while (l <= r) {
    mid = (l + r) >> 1;
    res = 0;
    dfs(rt, 0);
    if (res >= m)
      l = mid + 1, ans = mid;
    else
      r = mid - 1;
  }
  printf("%d\n", ans);
  return 0;
}
