#include <bits/stdc++.h>
using namespace std;
const int MAXN = 200000 + 5;
vector<int> g[MAXN];
int b[MAXN];
int n, k;
long long ans = 0;
long long dfs(int v, int p) {
long long sum = b[v];
if (sum > k) {
ans++;
return 0;
}
for (int u : g[v]) {
if (u == p) continue;
long long child = dfs(u, v);
if (sum + child > k) {
ans++;
} else {
sum += child;
}
}
return sum;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n >> k;
for (int i = 1; i <= n; i++)
cin >> b[i];
for (int i = 0; i < n - 1; i++) {
int x, y;
cin >> x >> y;
g[x].push_back(y);
g[y].push_back(x);
}
dfs(1, -1);
cout << ans << "\n";
return 0;
}
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