#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define F first
#define S second
#define pb push_back
#define endl "\n"
#define all(x) x.begin(), x.end()
const int M = 200007;
const ll inf = 2e9;
const ll mod = 1e9 + 7;
const double pi = acos(-1);
const double eps = 1e-6;
const int dx[] = {0, -1, 0, 1}, dy[] = {1, 0, -1, 0};
const int block = 320;
vector <int> adj[M];
ll n, k, a[M], ans;
ll dfs(int node, int p){
vector <ll> v;
for(auto i : adj[node]) if(i != p) v.pb(dfs(i, node));
ll ret = a[node];
sort(all(v));
for(auto i : v)
if(ret + i <= k) ret += i;
else ++ans;
return ret;
}
int main(){
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n >> k;
for(int i = 1; i <= n; ++i) cin >> a[i];
for(int i = 1; i < n; ++i){
int v, u;
cin >> v >> u;
adj[v].pb(u);
adj[u].pb(v);
}
dfs(1, 0);
cout << ans << endl;
return 0;
}
