#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 5;
int n, k, a[N];
vector <int> g[N];
pair <int, int> dfs(int u, int p) {
pair <int, int> res(0, a[u]);
vector <int> rem;
for (int v : g[u]) {
if (v == p) continue;
pair <int, int> tmp = dfs(v, u);
res.first += tmp.first;
rem.push_back(tmp.second);
}
sort(rem.begin(), rem.end());
for (int w : rem)
if (res.second + w <= k)
res.second += w;
else res.first++;
return res;
}
void input() {
cin >> n >> k;
for_each(a + 1, a + n + 1,
[](int &x) {cin >> x;});
for (int i = 1; i < n; i++) {
int u, v; cin >> u >> v;
g[u].push_back(v);
g[v].push_back(u);
}
}
void output() {
cout << dfs(1, 0).first << '\n';
}
int main() {
cin.tie(0)->sync_with_stdio(0);
input(); output();
}
