dfs

#include <iostream>
#include <cstdio>
#include <vector>
#define task "dfs"
using namespace std;
using ll = long long;
using ld = long double;

const int Inf = 1e9 + 7;
const int N = 4e5 + 5;
int n, k, l, cntno[N];
int v[N], cnt[N], dp[N][4], cnt1[N];
bool vis[N], ck[N];
vector<int> adj[N];

void Read()
{
    cin >> n >> k;
    for (int i = 1; i <= n; ++i)
        cin >> v[i];
    for (int i = 1; i < n; ++i)
    {
        int u, v;
        cin >> u >> v;
        adj[u].emplace_back(v);
        adj[v].emplace_back(u);
    }
}

void dfscnt(int v)
{
    vis[v] = 1;
    cnt[v] = 1;
    bool flag(0);
    for (auto i : adj[v])
        if (!vis[i])
        {
            if (ck[i])
            {
                dfscnt(i);
                if (cnt[i] == 0)
                    flag = 1;
                else
                    cnt[v] += cnt[i];
                cntno[v] += cntno[i];
                vis[i] = 0;
            }
            else
            {
                flag = 1;
                ++cntno[v];
            }
        }
    cnt1[v] = cnt[v];
    if (flag)
        cnt[v] = 0;
}

void dfs(int v, const int &root)
{
    vis[v] = 1;
    cnt[v] = 1;
    bool flag(0);
    int max1(0), max2(0);
    for (auto i : adj[v])
        if (!vis[i])
        {
            if (ck[i])
            {
                dfs(i, root);
                if (cnt[i] == 0)
                {
                    flag = 1;
                    dp[v][1] = max(dp[v][1], dp[i][1] + (cntno[i] == cntno[root]) * cnt1[v]);
                    if (max1 < dp[i][0])
                    {
                        max2 = max1;
                        max1 = dp[i][0];
                    }
                    else if (max2 < dp[i][0])
                        max2 = dp[i][0];
                }
                else
                    cnt[v] += cnt[i];
                dp[v][3] = max(dp[v][3], dp[i][3]);
            }
            else
            {
                flag = 1;
            }
        }
    dp[v][3] = max(dp[v][3], cnt[v]);
    if (flag)
    {
        dp[v][0] = max1 + cnt[v];
        dp[v][1] = max(dp[v][1], max1 + max2 + cnt[v]);
        cnt[v] = 0;
    }
}

bool Check(int val)
{
    for (int i = 1; i <= n; ++i)
    {
        vis[i] = 0;
        ck[i] = v[i] >= val;
        cnt[i] = cnt1[i] = cntno[i] = dp[i][0] = dp[i][1] = dp[i][3] = 0;
    }
    vector<int> s;
    s.reserve(n);
    for (int i = 1; i <= n; ++i)
        if (!ck[i])
            for (auto j : adj[i])
                if (ck[j])
                    s.emplace_back(j);
    if (s.empty())
        for (int i = 1; i <= n; ++i)
            if (ck[i])
            {
                s.emplace_back(i);
                break;
            }
    for (auto i : s)
        if (!vis[i])
        {
            dfscnt(i);
            dfs(i, i);
            //cout << i << " " << dp[i][1] << " " << dp[i][0] << " " << dp[i][3] << "\n";
            if (dp[i][1] >= k || dp[i][0] >= k || dp[i][3] >= k)
                return true;
        }
    return false;
}

void Solve()
{
    int l = 1, m, h = 1e6;
    while (l <= h)
    {
        m = (l + h) / 2;
        if (Check(m))
            l = m + 1;
        else
            h = m - 1;
    }
    cout << h;
}

int32_t main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    if (fopen(task ".INP", "r"))
    {
        freopen(task ".INP", "r", stdin);
        freopen(task ".OUT", "w", stdout);
    }
    Read();
    Solve();
}