#include<bits/stdc++.h>
//#pragma GCC optimize("Ofast,unroll-loops")
//#pragma GCC target("avx2,popcnt,lzcnt,abm,bmi,bmi2,fma,tune=native")
#define pii pair<int, int>
#define fi first
#define se second
#define pb push_back
#define int long long
#define ld long double
using namespace std;
using ll=long long;
const int inf = 1e9;
const int MN =2e5+5;
const int mod=998244353;
int n,k;
vector<int> adj[MN];
vector<pii> g[MN];
int a[MN];
pii dp[MN];
void dfs(int u, int p) {
int sum=a[u], cnt=0;
for (int v:adj[u]) {
if(v==p) continue;
dfs(v,u);
g[u].pb(dp[v]);
cnt+=dp[v].se;
sum+=dp[v].fi;
}
if(g[u].size()==0) return;
sort(g[u].begin(), g[u].end());
while(sum>k) {
cnt++;
sum-=g[u].back().fi;
g[u].pop_back();
}
dp[u]={sum,cnt};
// cout<<u<<" "<<dp[u].fi<<" "<<dp[u].se<<"\n";
}
void solve() {
cin>>n>>k;
for (int i=1; i<=n; i++) {
cin>>a[i];
dp[i].fi=a[i];
}
for (int i=1; i<n; i++) {
int x,y;
cin>>x>>y;
adj[x].pb(y);
adj[y].pb(x);
}
dfs(1,0);
cout<<dp[1].se;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
// freopen(".inp", "r", stdin);
// freopen(".out", "w", stdout);
int t=1;
// cin>>t;
while(t--) {
solve();
}
}
