#include <bits/stdc++.h>
#define ll long long
#define pb push_back
#define all(x) x.begin(),x.end()
#define ld long double
using namespace std;
const ll sz=1e5+100;
vector<ll>v[sz];
vector<array<ll,2>>edges;
ll used[sz],h[sz],cnt;
void dfs(ll u)
{
used[u]=1;
cnt+=h[u];
for(auto to:v[u]){
if(used[to]) continue;
dfs(to);
}
}
int main()
{
ll n,k;cin>>n>>k;
ll pre[n+5];
pre[0]=0;
for(int i=1;i<=n;i++){
cin>>h[i];
pre[i]=pre[i-1]+h[i];
}
for(int i=1;i<n;i++){
ll a,b;cin>>a>>b;
edges.pb({a,b});
}
ll ans=n-1;
for(int mask=0;mask<(1<<(n-1));mask++){
vector<array<ll,2>>v1;
ll num=n-1;
for(int j=0;j<n-1;j++){
if(mask&(1<<j)){
v1.pb({edges[j][0],edges[j][1]});num--;
}
}
for(int i=0;i<=n;i++){
used[i]=0;v[i].clear();
}
for(auto [to1,to2]:v1){
v[to1].pb(to2);
v[to2].pb(to1);
}
ll ok=0;
for(int i=1;i<=n;i++){
if(used[i]==0){
cnt=0;
dfs(i);
if(cnt>k){ok=1;break;}
}
}
if(ok==0){
ans=min(ans,num);
}
}
cout<<ans<<endl;
}
