#include <bits/stdc++.h>
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
//#define int long long
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int mod = 1e9 + 7;
const int LOG = 20;
const int maxn = 1e5 + 5;
const double eps = 1e-9;
ll sub[maxn+5], n, k, ans = 0, val[maxn+5];
vector<int> graph[maxn];
void dfs(int u, int p) {
sub[u] = val[u];
vector<ll> vec;
for(int &v : graph[u]) {
if(v == p) continue;
dfs(v, u);
vec.push_back(sub[v]);
sub[u] += sub[v];
}
if(sub[u] > k) {
sort(all(vec));
ll sum = val[u];
for(ll &x : vec) {
if(sum + x > k) {
ans++;
sub[u] -= x;
} else {
sum += x;
}
}
}
}
int32_t main() {
cin >> n >> k;
for(int i=1; i<=n; i++) cin >> val[i];
for(int i=0; i<n-1; i++) {
int a, b;
cin >> a >> b;
graph[a].push_back(b);
graph[b].push_back(a);
}
dfs(1, 1);
cout << ans << '\n';
return 0;
}
