#include <bits/stdc++.h>
#define FOR(i, u, v) for (int i = u; i <= v; i++)
#define FORD(i, v, u) for (int i = v; i >= u; i--)
#define ll long long
#define pii pair<int, int>
#define PB push_back
#define mp make_pair
#define F first
#define S second
#define N 100005
#define maxc 1000000
using namespace std;
int n, k, res;
vector<int> a[N];
vector<ll> vv[N];
ll val[N];
void DFS(int u, int p)
{
for (auto v : a[u])
{
if (v == p) continue;
DFS(v, u);
val[u] += val[v];
vv[u].PB(val[v]);
}
sort(vv[u].begin(), vv[u].end());
reverse(vv[u].begin(), vv[u].end());
for (auto v : vv[u])
{
if (val[u] <= k) break;
res++;
val[u] -= v;
}
}
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
//freopen("INP.TXT", "r", stdin);
//freopen("OUT.TXT", "w", stdout);
cin >> n >> k;
FOR(i, 1, n) cin >> val[i];
FOR(i, 2, n)
{
int u, v; cin >> u >> v;
a[u].PB(v);
a[v].PB(u);
}
DFS(1, -1);
cout <<res;
}
