#include <bits/stdc++.h>
#define int long long
using namespace std;
typedef long long ll;
const ll INF = 1e18;
const int maxn = 1e6 + 5;
const int mod = 1e9 + 7;
using pi = pair<ll, ll>;
using vi = vector<ll>;
using pii = pair<pair<ll, ll>, ll>;
#define all(x) x.begin(), x.end()
#define len(x) ll(x.size())
#define eb emplace_back
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define MIN(v) *min_element(all(v))
#define MAX(v) *max_element(all(v))
int dp[100005];
vector<int> G[100005];
int ans = 0;
int n;
int a[100005];
int root;
int k;
priority_queue<int> pq[100005];
int dfs(int u, int p)
{
dp[u] = a[u];
for (auto v : G[u])
{
if (v == p)
continue;
int d = dfs(v, u);
pq[u].push(d);
dp[u] += d;
while (dp[u] > k)
{
dp[u] -= pq[u].top();
pq[u].pop();
ans++;
}
}
return dp[u];
}
signed main()
{
cin >> n >> k;
for (int i = 1; i <= n; i++)
{
cin >> a[i];
}
for (int i = 1; i <= n - 1; i++)
{
int x, y;
cin >> x >> y;
G[x].push_back(y);
G[y].push_back(x);
}
dfs(1, 1);
cout << ans;
}
