#include <bits/stdc++.h>
#define pb push_back
using namespace std;
const int MAXN = 100000;
int n, k;
int a, b;
int cnt;
int v[MAXN+1];
int deg[MAXN+1];
bool vis[MAXN+1];
vector <int> path[MAXN+1];
void DFS(int now, int par) {
vis[now] = 1;
for (int i : path[now]) {
if (vis[i] || i == par) continue;
if (v[now] + v[i] > k) cnt++;
else v[i] += v[now];
deg[i]--;
if (deg[i] == 1) DFS(i, now);
}
}
signed main() {
ios_base::sync_with_stdio(0), cin.tie(0);
cin >> n >> k;
for (int i = 1; i <= n; i++)
cin >> v[i];
for (int i = 1; i < n; i++) {
cin >> a >> b;
path[a].pb(b), deg[a]++;
path[b].pb(a), deg[b]++;
}
for (int i = 1; i <= n; i++)
if (deg[i] == 1 && !vis[i]) DFS(i, 0);
cout << cnt << "\n";
}
