#include <bits/stdc++.h>
#define ll long long
#define vll vector<ll>
#define vllp vector<pair<ll, ll> >
#define vi vector <int>
#define vip vector <pair <int, int> >
#define db double
#define ldb long double
#define pdb pair <double, double>
#define YES cout<<"YES"
#define NO cout<<"NO"
#define endl cout<<endl
#define vv vector <vector <ll> >
#define pll pair <ll, ll>
#define pi pair <int, int>
#define pb push_back
#define f first
#define s second
using namespace std;
const ll mod=1e9+7;
const ll modx=998244353;
const double eps=1e-9;
const ll INF=INT_MAX;
const ll INFINF=LLONG_MAX;
const ll N=1e5;
ll n, k, ans;
ll price[N+5];
vll v[N+5];
void input()
{
cin >> n >> k;
for(int i = 1; i <= n; i++)
{
cin >> price[i];
}
for(int i = 1; i < n; i++)
{
ll x, y;
cin >> x >> y;
v[x].pb(y);
v[y].pb(x);
}
}
void dfs(ll u, ll pa)
{
vll vc;
for(auto i: v[u])
{
if(i==pa) continue;
dfs(i, u);
vc.pb(price[i]);
}
sort(vc.begin(), vc.end());
for(auto i: vc)
{
if(price[u]+i<=k) price[u]+=i, ans++;
else break;
}
}
void solve()
{
dfs(1, 0);
cout << n-1-ans;
}
int main()
{
srand(time(0));
// auto start_time = chrono::high_resolution_clock::now();
// freopen("test.txt", "r", stdin);
// freopen("out.txt", "w", stdout);
// ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
int t=1;
while(t--)
{
input();
solve();
}
// auto end_time = chrono::high_resolution_clock::now();
// double duration = chrono::duration_cast<chrono::milliseconds>(end_time - start_time).count();
// cout << "\n[ " << duration << " ms ]\n";
}
/*
7
1 1 1 1 1 2 3
*/
