//Author RufatM
#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/detail/standard_policies.hpp>
using namespace __gnu_pbds;
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef vector<ll> vll;
typedef vector<bool> vb;
typedef vector<string> vs;
#define fastio ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define endl '\n'
#define pb push_back
#define pf push_front
#define eb emplace_back
#define ff first
#define ss second
#define all(x) begin(x),end(x)
#define rall(x) rbegin(x),rend(x)
#define mt19937_64 mt_rand(chrono::steady_clock::now().time_since_epoch().count())
#define ordered_set tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update>
const int MOD=1000000007;
const int INF=1000000007;
const ll LINF=4e18;
const int MAXN=100005;
ll n,k;
ll dp[MAXN+1];
vi g[MAXN+1];
ll ans;
ll dfs(int u,int p){
vll children;
for(int v:g[u]){
if(v==p){
continue;
}
ll sub = dfs(v,u);
children.pb(sub);
}
ll sum = dp[u];
sort(all(children));
for(ll sub:children){
if(sum+sub<=k){
sum+=sub;
}
else{
ans++;
}
}
return sum;
}
signed main(){
fastio;
#ifndef ONLINE_JUDGE
//freopen("input.txt","r",stdin);
//freopen("output.txt","w",stdout);
#endif
int t=1;
//cin >> t;
while(t--){
cin >> n >> k;
for(int i=1;i<=n;i++){
cin >> dp[i];
}
for(int i=0;i<n-1;i++){
int x,y;
cin >> x >> y;
g[x].pb(y);
g[y].pb(x);
}
ans = 0;
dfs(1,0);
cout << ans << endl;
}
}
