#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define vii vector<pair<int, int>>
#define vi vector<int>
#define vl vector<long long>
#define vll vector<pair<long long, long long>>
#define mp make_pair
#define pb push_back
#define rep(i, a, b) for(int i = a;i<=(b);i++)
#define f first
#define s second
#define FIO ios_base::sync_with_stdio(0);cin.tie(0);
#define start int tt;cin>>tt;rep(testcase, 1, tt)
#define print(k) cout<<"Case #"<<testcase<<": "<<k<<"\n";
#define endl "\n"
#define int long long
#define DEBUG(k) cerr<<k<<"\n";
vector<int> w(100010, 0);
int ans = 0, n, k;
vector<int> g[100010];
int s[100010], a[100010];
void dfs(int v,int p)
{
s[v]=a[v];
vector <long long> q;
for(auto x:g[v])
{
if(x!=p)
{
dfs(x,v);
s[v]+=s[x];
q.push_back(s[x]);
}
}
sort(q.begin(),q.end());
auto it = q.end();
it--;
while(s[v]>k)
{
s[v]-=*it;
ans++;
it--;
}
}
void solve() {
cin >> n >> k;
rep(i, 1, n)cin>>a[i];
rep(i, 0, n-2) {
int x, y;
cin >> x >> y;
g[x].push_back(y);
g[y].push_back(x);
}
dfs(1, 0);
cout<<ans<<endl;
}
int32_t main () {/*
#ifndef ONLINE_JUDGE
freopen("stdin", "r", stdin);
freopen("stdout", "w", stdout);
freopen("stderr", "w", stderr);
#endif*/
int t = 1;
//cin >> t;
while(t--) {
solve();
}
return 0;
}
