#include <bits/stdc++.h>
using namespace std;
#define int long long int
#define ins insert
#define pb push_back
#define endl '\n'
#define putr(x) cout<<x<<endl;return;
#define all(x) x.begin(),x.end()
const int mod = 1e9 +7, sze = 1e5 +5, inf = INT_MAX, LL = 30;
int k ;
pair<int,int> dp[sze];
int val[sze];
vector<int> graph[sze];
void dfs(int node,int par=-1){
for(auto v:graph[node]){
if(v!=par){
dfs(v,node);
}
}
vector<int> lst;
int sum=val[node];
for(auto v:graph[node]){
if(v!=par){
dp[node].first += dp[v].first;
lst.pb(dp[v].second);
sum+=dp[v].second;
}
}
sort(all(lst));
while(sum>k){
sum-=lst.back();
dp[node].first ++;
}
dp[node].second = sum;
}
void rush(){
int n;
cin>>n>>k;
for(int i=1;i<=n;i++){
cin>>val[i];
}
for(int i =1;i<n;i++){
int u,v;
cin>>u>>v;
graph[u].pb(v);
graph[v].pb(u);
}
dfs(1);
putr(dp[1].first);
}
signed main(){
ios::sync_with_stdio(0);
cin.tie(0);
int tt = 1;
// cin>>tt;
while(tt--){
rush();
}
return 0;
}
