// author - alimammadzade
#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 1;
int p[N];
int _find(int u) {
return (p[u] < 0 ? u : p[u] = _find(p[u]));
}
void _union(int u, int v) { p[u] += p[v]; p[v] = u; }
signed main() {
// cin.tie(nullptr)->sync_with_stdio(0);
// system("cls"), freopen("in.txt", "r", stdin);
int n, k;
cin >> n >> k;
for (int i = 1; i <= n; i++) { cin >> p[i]; p[i] = -p[i]; }
int res = 0;
vector<array<int, 2>> e(n - 1);
for (auto& [u, v] : e) {
cin >> u >> v;
int pu = _find(u), pv = _find(v);
if (pu != pv and -p[pu] - p[pv] <= k) _union(pu, pv);
}
for (auto& [u, v] : e) res += (_find(u) != _find(v));
cout << res;
}
