#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll mx=1e5+10;
const int mod= 1e9+7 ;
const ll inf=1e9+5;
//***while there is life there is hope
int n,m,k;
int siz[mx];int ans;
vector<int> adj[mx];
int arr[mx];
int vis[mx];
int dfs(int node){
vis[node]=1;
vector<int>v;
for(auto it:adj[node]){
if(vis[it]){continue;}
v.push_back(dfs(it));
}
int ret=arr[node];
sort(v.begin(),v.end());
for(auto it:v){
if(ret+it<=k){
ret+=it;
}else{
ans++;
}
}
return ret;
}
int main() {
cin>>n>>k;int sum2=0;
for(int i=1;i<=n;i++){
cin>>arr[i];sum2+=arr[i];
}
for(int i=0;i<n-1;i++){
int a,b;cin>>a>>b;
adj[a].push_back(b);
adj[b].push_back(a);
}
dfs(1);
cout<<ans;
}
