#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ll long long
#define endl "\n"
using namespace std;
using namespace __gnu_pbds;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
template <typename T, typename key = less_equal<T>>
using ordered_set = tree<T, null_type, key, rb_tree_tag, tree_order_statistics_node_update>;
const ll N = 1e5 + 5;
vector<ll> g[N];
ll a[N], cur[N], k, ans = 0;
void dfs(ll v, ll par = 0)
{
vector<ll> vals;
cur[v] = a[v];
for (ll to : g[v])
if (to != par) dfs(to, v), vals.push_back(cur[to]);
sort(vals.begin(), vals.end());
for (ll i : vals)
if (i + cur[v] > k) ans++;
else cur[v] += i;
}
void solve()
{
ll n;
cin >> n >> k;
for (ll i = 1; i <= n; i++) cin >> a[i];
for (ll i = 1; i < n; i++)
{
ll a, b;
cin >> a >> b;
g[a].push_back(b);
g[b].push_back(a);
}
dfs(1);
cout << ans << endl;
}
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0);
ll t = 1;
// precomp();
// cin >> t;
for (ll cs = 1; cs <= t; cs++)
solve();
// cerr << "\nTime elapsed: " << clock() * 1000.0 / CLOCKS_PER_SEC << " ms\n";
}
