#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O3")
#define ll long long
#define fori(i,j,k) for(ll i=j; i<=k;i++)
#define study ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define pb push_back
#define all(s) s.begin(),s.end()
#define ins insert
#define ss second
#define ff first
ll sz=2e5+10;
ll INF=1e12;
ll mod=1e9+7;
ll n,k;
vector<ll>subt(sz,-1),a(sz,-1),check(sz,0);
vector<vector<ll>>g(sz);
ll ans=0;
void dfs(ll t,ll par=-1){
check[t]=1;
subt[t]=a[t];
priority_queue<ll>so;
for(auto x: g[t]){
if(x==par)
continue;
dfs(x,t);
subt[t]+=subt[x];
so.push(subt[x]);
}
while(subt[t]>k){
ans++;
subt[t]-=so.top();
so.pop();
}
}
void work(){
cin>>n>>k;
fori(i,1,n){
cin>>a[i];
}
fori(i,1,n-1){
ll a,b;
cin>>a>>b;
g[a].pb(b);
g[b].pb(a);
}
dfs(1,-1);
cout<<ans<<endl;
}
int main()
{
study;
ll t=1;
//cin>>t;
fori(i,1,t)
work();
}
/*
*/
