#include <bits/stdc++.h>
using namespace std;
void dfs(const vector<vector<int>> &graph, vector<char> &visited, int node,
int &sum, const vector<int> &values) {
visited[node] = true;
sum += values[node];
for (size_t i = 0; i < graph.size(); i++) {
if (graph[node][i] and !visited[i]) {
dfs(graph, visited, i, sum, values);
}
}
}
int main() {
int n, k, x, y, s, ans;
vector<int> h;
vector<pair<int, int>> e;
vector<vector<int>> g;
vector<char> v;
cin >> n >> k;
g.resize(n, vector<int>(n, 0));
h.resize(n);
ans = n - 1;
for (int &s : h) {
cin >> s;
}
for (int i = 0; i < n - 1; i++) {
cin >> x >> y;
e.emplace_back(x - 1, y - 1);
}
sort(e.rbegin(), e.rend(),
[&h](const pair<int, int> &p1, const pair<int, int> &p2) -> bool {
return h[p1.first] + h[p1.second] < h[p2.first] + h[p2.second];
});
for (int i = 0; i < n - 1; i++) {
x = e[i].first, y = e[i].second;
v.assign(n, false);
s = 0;
g[x].push_back(y);
g[y].push_back(x);
for (int i = 0; i < n; i++) {
if (!v[i]) {
dfs(g, v, i, s, h);
if (s >= k) {
goto end;
}
}
}
ans = n - 1 - i;
}
end:
cout << ans << '\n';
return 0;
}
