#include <bits/stdc++.h>
#ifdef ULVI
#define db(x) cerr<<"[ "<<#x<<" = "<<(x)<<" ]\n"
#define dbv(v) cerr<<#v<<" = [ ";for(auto &__x : v)cerr<<__x<<' ';cerr<<"]\n"
#define line() cerr<<string(80, '-')<<'\n'
#else
#define db(x)
#define dbv(v)
#define line()
#endif
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define ff first
#define ss second
#define enld endl
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef pair<ll,ll> pll;
const ll sz=2e5+100;
const ll mod=1e9+7;
const ll inf=1e18;
template<class T>
using indexed_set=tree<T,null_type,less<T>,rb_tree_tag,tree_order_statistics_node_update>;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
vector<ll> v(sz),comp(sz),g[sz];
ll ans=0;
ll n,k;
void dfs(ll node,ll p,ll c){
for(ll i:g[node]){
if(i==p) continue;
if(comp[c]+v[i]>k){
ans++;
comp[c+1]=v[i];
dfs(i,node,c+1);
}
else{
comp[c]+=v[i];
dfs(i,node,c);
}
}
}
void solve(){
cin>>n>>k;
for(ll i=1;i<=n;i++) cin>>v[i];
for(ll i=1;i<n;i++){
ll a,b;
cin>>a>>b;
g[a].push_back(b);
g[b].push_back(a);
}
for(ll i=1;i<=n;i++){
sort(all(g[i]),[](ll a,ll b){
return v[a]<v[b];
});
}
comp[0]=v[1];
dfs(1,0,0);
cout<<ans<<'\n';
}
int main(){
//freopen("input.txt","r",stdin);
//freopen("output.txt","w",stdout);
ios_base::sync_with_stdio(0);
cin.tie(0);
ll t=1;
//cin>>t;
for(ll _=1;_<=t;_++){
//cout<<"Scenario #"<<_<<":\n";
solve();
}
}
