#include <bits/stdc++.h>
using namespace std;
#define lesgooo ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0)
#define endl '\n'
#define int long long
vector<int> par, sum, sz;
int n, x, y, k;
int find(int u) {return par[u] = (u == par[u]? u : find(par[u]));}
int unionn(int u, int v)
{
u = find(u), v = find(v);
if (sum[u]+sum[v] > k) return 1;
if (sz[u] < sz[v]) swap(u, v);
sz[u]+=sz[v], par[v] = u, sum[u]+=sum[v];
return 0;
}
signed main()
{
lesgooo;
cin >> n >> k;
par.resize(n), sum.resize(n), sz.resize(n);
for (int i =0 ; i < n; i++) cin >> sum[i], par[i] = i, sz[i] = 1;
int ans =0 ;
for (int i = 0; i < n-1; i++) cin >> x >> y, ans+=unionn(--x, --y);
cout << ans;
return 0;
}
