#include <bits/stdc++.h>
#define ll long long
using namespace std;
#define f first
#define s second
#define pb push_back
#define ep emplace
#define eb emplace_back
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define uniquev(v) sort(all(v)), (v).resize(unique(all(v)) - (v).begin())
#define mem(f,x) memset(f , x , sizeof(f))
#define sz(x) (int)(x).size()
#define __lcm(a, b) (1ll * ((a) / __gcd((a), (b))) * (b))
#define mxx *max_element
#define mnn *min_element
#define cntbit(x) __builtin_popcountll(x)
#define len(x) (int)(x.length())
const int N = 1e5 + 10;
vector <int> ed[N];
ll n, k, a[N];
pair <ll, ll> dp[N];
void dfs(int u, int v) {
int ans = 0;
vector <int> lst;
for (auto x : ed[u]) {
if (x == v)
continue;
dfs(x, u);
ans += dp[x].f;
lst.pb(dp[x].s);
}
int sum = a[u];
sort(all(lst));
for (auto x : lst) {
if (sum + x <= k) {
sum += x;
ans++;
}
}
dp[u].f = ans;
dp[u].s = sum;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n >> k;
for (int i = 1; i <= n; i++)
cin >> a[i];
for (int i = 1; i < n; i++) {
int a, b;
cin >> a >> b;
ed[a].pb(b);
ed[b].pb(a);
}
dfs(1, 1);
cout << n - dp[1].f - 1 << '\n';
return 0;
}
