#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() {
bool bruteForce = true;
int n, k, s = 0, ans = INT_MAX;
cin >> n >> k;
vector<int> h(n);
vector<pair<int, int>> e(n - 1);
for (int &s : h) {
cin >> s;
}
for (auto &[a, b] : e) {
cin >> a >> b;
a--;
b--;
if (a + 1 != b) {
bruteForce = false;
}
}
if (bruteForce) {
ans = 0;
for (int i = 0; i < n; i++) {
s += h[i];
if (s > k) {
ans++;
s = h[i];
}
}
cout << ans << '\n';
return 0;
}
vector<vector<int>> allPermutations;
vector<int> arr = {1, 2, 3, 4, 5, 6, 7, 8, 9,
10, 11, 12, 13, 14, 15, 16, 17, 18};
do {
allPermutations.push_back(arr);
} while (next_permutation(arr.begin(), arr.end()));
for (int c = 0; c <= n - 1; c++) {
for (const vector<int> &road : allPermutations) {
unordered_set<int> cuts;
vector<vector<int>> g(n, vector<int>(n, false));
vector<char> v(n, false);
for (int i = 0; i < c; i++) {
cuts.insert(road[i]);
}
for (const auto &[a, b] : e) {
g[a][b] = true;
g[b][a] = true;
}
int s = 0;
for (int i = 0; i < n; i++) {
if (!v[i]) {
dfs(g, v, i, s, h);
if (s >= k) {
goto next;
}
}
}
ans = min(ans, c);
next:
continue;
}
}
cout << ans << '\n';
}
