#include <bits/stdc++.h>
#define FOR(i, x, y) for (int i = x; i < y; i++)
typedef long long ll;
using namespace std;
int n, k;
ll a[100001];
vector<int> graph[100001];
int dfs(int node = 1, int parent = 0) {
priority_queue<ll> pq;
int ans = 0;
for (int i : graph[node]) if (i != parent) {
ans += dfs(i, node);
pq.push(a[i]);
a[node] += a[i];
}
while (a[node] > k) {
ans++;
a[node] -= pq.top();
pq.pop();
}
return ans;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n >> k;
FOR(i, 1, n + 1) cin >> a[i];
FOR(i, 1, n) {
int u, v;
cin >> u >> v;
graph[u].push_back(v);
graph[v].push_back(u);
}
cout << dfs();
return 0;
}
