// comp = compile
// compr = compile & run
// in terminal, gocp goes to cp directory

#include <bits/stdc++.h>
using namespace std;

#include <bits/extc++.h>
using namespace __gnu_pbds;
using ll = int;

using ordered_set = tree<ll, null_type, less_equal<ll>, rb_tree_tag, tree_order_statistics_node_update>;
using pl = pair<ll, ll>;
#define f first
#define s second

ll n, m;
vector<ll> adj[105];
ll dp[105][105][105];
ll dp2[105][105][105];
ll sz[105];
ll a[105];

void dfs(ll v, ll p) {
    sz[v] = 1;
    vector<ll> ch;
    for (ll x: adj[v]) if (x != p) {
        dfs(x, v);
        ch.push_back(x);
        sz[v] += sz[x];
    }

    memset(dp2[0], 1, sizeof dp2[0]);
    dp2[0][0][0] = 0;

    ll s = 0;
    for (ll i = 0; i < ch.size(); i++) {
        ll x = ch[i];

        memset(dp2[i + 1], 1, sizeof dp2[i + 1]);

        for (ll a = 0; a <= s; a++) {
            for (ll b = 0; b <= s; b++) {
                for (ll c = 0; c <= sz[x]; c++) {
                    for (ll d = 0; d <= sz[x]; d++) {
                        ll td = (a > 0 ? b + 1 : -n) + (c > 0 ? d + 1 : -n);
                        ll cd = max(b, d);
                        dp2[i + 1][a + c][cd] = min(dp2[i + 1][a + c][cd], max(td, max(dp2[i][a][b], dp[x][c][d])));
                    }
                }
            }
        }

        s += sz[x];
    }

    memset(dp[v], 1, sizeof dp[v]);

    for (ll i = 0; i <= n; i++) for (ll j = 0; j <= n; j++) {
        if (i == 0) dp[v][i][j] = min(dp[v][i][j], dp2[ch.size()][i][j]);
        else if (j > 0) dp[v][i][j] = min(dp[v][i][j], dp2[ch.size()][i][j - 1]);
    }

    // cout << v << " " << dp[v][1][1] << " " << dp[v][1][0] << " " << dp[v][2][0] << " " << dp[v][2][1] << '\n';

    if (a[v] == 1) for (ll i = sz[v]; i >= 0; i--) for (ll j = 0; j <= sz[v]; j++) {
        // cout << i << " " << j << " " << dp[v][i][j] << '\n';
        dp[v][i + 1][j] = min(dp[v][i + 1][j], max(dp[v][i][j], j));
        // cout << i << " " << j << " " << dp[v][i + 1][j] << '\n';
    }

    // cout << "V " << v << " " << a[v] << '\n';
    // for (ll i = 0; i <= sz[v]; i++) {
    //     for (ll j = 0; j <= sz[v]; j++) {
    //         cout << i << " " << j << " " << dp[v][i][j] << '\n';
    //     }
    // }
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    cin >> n >> m;
    for (ll i = 0; i < n; i++) cin >> a[i];

    for (ll i = 0; i < n - 1; i++) {
        ll x, y;
        cin >> x >> y;
        --x; --y;
        adj[x].push_back(y);
        adj[y].push_back(x);
    }

    dfs(0, -1);

    ll ans = 1e9;
    for (ll i = 0; i <= n; i++) ans = min(ans, dp[0][m][i]);
    cout << ans << '\n';
}