// Author RufatM
#include <bits/stdc++.h>
using namespace std;
#define MOD 1000000007
#define INF 1e9+7
#define ll long long
#define ull unsigned long long
#define vi vector<int>
#define vii vector<vector<int>>
#define mii map<int,int>
#define pb push_back
#define pii pair<ll,int>
#define all(a) a.begin(),a.end()
#define fastio ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
const int MAXN = 100005;
vector<int> tree[MAXN];
int h[MAXN];
int k;
int cuts = 0;
int dfs(int u, int parent) {
int total_spice = h[u];
for (int v : tree[u]) {
if (v != parent) {
int child_spice = dfs(v, u);
if (total_spice + child_spice > k) {
cuts++;
total_spice = h[u];
}
else {
total_spice += child_spice;
}
}
}
return total_spice;
}
signed main() {
fastio;
int n;
cin >> n >> k;
for (int i = 1; i <= n; i++) {
cin >> h[i];
}
for (int i = 0; i < n - 1; i++) {
int u, v;
cin >> u >> v;
tree[u].pb(v);
tree[v].pb(u);
}
dfs(1, 0);
cout << cuts << '\n';
}
