#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll INF=1e18;
const int maxn=1e6+5;
const int mod=1e9+7;
using pi=pair<ll,ll>;
using vi=vector<ll>;
using pii=pair<pair<ll,ll>,ll>;
#define all(x) x.begin(), x.end()
#define len(x) ll(x.size())
#define eb emplace_back
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define MIN(v) *min_element(all(v))
#define MAX(v) *max_element(all(v))
int dp[100005];
vector<int>G[100005];
int ans=0;
int n;
int a[100005];
int root;
int k;
priority_queue<int>pq[100005];
int dfs(int u,int p){
dp[u]=a[u];
for(auto v:G[u]){
if(v==p)continue;
int d=dfs(v,u);
pq[u].push(d);
dp[u]+=d;
if(dp[u]>k){
dp[u]-=pq[u].top();
pq[u].top();
ans++;
}
}
return dp[u];
}
signed main(){
cin>>n>>k;
for(int i=1;i<=n;i++){
cin>>a[i];
}
for(int i=1;i<=n-1;i++){
int x,y;
cin>>x>>y;
G[x].push_back(y);
G[y].push_back(x);
}
dfs(1,1);
cout<<ans;
}
