#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#endif
#define ll long long
#define int ll
#define ui unsigned int
#define pb push_back
#define ull unsigned long long
#define ld long double
#define pii pair<int,int>
#define all(x) (x).begin(), (x).end()
#define isz(x) (int)(x.size())
#define vi vector<int>
#define ost tree<pii, null_type, less<pii>, rb_tree_tag, tree_order_statistics_node_update>
// mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
const int sz = 1e6, inf = 1e9;
const ll mod = 998244353, INF = 1e18;
vi g[sz];
int a[sz], ans = 0, n, k;
int dfs(int u, int p){
int sm = a[u];
multiset<int> edges;
for (auto &v : g[u]) {
if (v == p) continue;
edges.insert(dfs(v, u));
}
for (auto &i : edges) {
if (sm + i > k) {
ans++;
continue;
}
sm += i;
}
return sm;
}
void solve(int tc) {
cin >> n >> k;
for (int i = 1; i <= n; i++) cin >> a[i];
for (int i = 1; i < n; i++) {
int u, v; cin >> u >> v;
g[u].pb(v);
g[v].pb(u);
}
dfs(1, -1);
cout << ans << "\n";
}
void precompute() {}
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
#ifdef LOCAL
freopen("in.txt", "r", stdin);
freopen("err.log", "w", stderr);
#endif
precompute();
int t = 1;
// cin >> t;
for (int tc = 1; tc <= t; tc++) solve(tc);
return 0;
}
