#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
const int N = 1e5 + 500;
int n, limit, a[N], total[N], pr[N];
vector <int> g[N];
int f(int x) { return (x == pr[x]) ? x : pr[x] = f(pr[x]); }
void unite(int x, int y) { pr[f(y)] = f(x); }
void dfs(int v, int pred = -1) {
for (int to : g[v]) {
if (to == pred)
continue;
int x = f(v), y = f(to);
if (total[x] + total[y] <= limit)
total[x] += total[y], unite(x, y);
dfs(to, v);
}
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n >> limit;
for (int i = 0; i < n; ++i)
cin >> a[i], pr[i] = i, total[i] = a[i];
for (int i = 0; i < n - 1; ++i) {
int x, y;
cin >> x >> y;
--x, --y;
g[x].push_back(y);
g[y].push_back(x);
}
dfs(0);
set <int> s;
s.clear();
for (int i = 0; i < n; ++i)
s.insert(f(i));
cout << int(s.size()) - 1 << "\n";
}
