#include <bits/stdc++.h>
using namespace std;
template<typename T1, typename T2>ostream& operator<<(ostream &os, const pair<T1, T2> &p) {return os << '{' << p.first << ", " << p.second << '}';}
template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator<<(ostream &os, const T_container &v) { os << '{'; string sep; for (const T &x : v) os << sep << x, sep = ", "; return os << '}'; }
template <typename K, typename V> ostream& operator<<(ostream& os, const map<K, V>& m) {os << "{";for (auto it = m.begin(); it != m.end(); ++it) {if (it != m.begin()) os << ", "; os << it->first << " : " << it->second;}return os << "}";}
void debug() { cerr << endl; }
template<typename Head, typename... Tail>
void debug(Head H, Tail... T) { cerr << H; debug(T...); }
#ifdef ONPC
#define deb(...) cerr << '[' << __FILE__ << ':' << __LINE__ << "] (" << #__VA_ARGS__ << "):", debug(__VA_ARGS__)
#else
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#define deb(...)
#endif
const int mxN = 2e5 + 5;
const int mod = 1e9 + 7;
const int dx4[] = {1, -1, 0, 0}, dy4[] = {0, 0, -1, 1};
const int dx8[] = {1, -1, 0, 0, 1, -1, 1, -1}, dy8[] = {0, 0, -1, 1, 1, -1, -1, 1};
set<int> g[mxN];
set<array<int64_t, 2>> leaf;
int64_t arr[mxN], cost[mxN];
void run_case() {
int n, k, ans = 0;
cin >> n >> k;
for (int i = 1; i <= n; i++) cin >> arr[i], cost[i] = arr[i];
for (int i = 1, u, v; i < n; i++) {
cin >> u >> v;
g[u].insert(v);
g[v].insert(u);
}
for (int i = 1; i <= n; i++)
if (g[i].size() == 1)
leaf.insert({arr[i], i});
while (!leaf.empty()) {
int64_t u = (*leaf.begin())[1], c = (*leaf.begin())[0];
leaf.erase({c, u});
if (!g[u].empty()) {
auto v = *g[u].begin();
g[u].clear();
g[v].erase(u);
if (cost[v] + cost[u] <= k) {
cost[v] += cost[u];
} else {
ans++;
}
if (g[v].size() == 1) {
leaf.insert({cost[v], v});
}
}
}
cout << ans << "\n";
// for (int i = 1; i <= n; i++) cout << cost[i] << " ";
return;
}
int main() {
cin.tie(nullptr)->sync_with_stdio(false);
int test_case = 1;
// cin >> test_case;
for (int num_case = 1; num_case <= test_case; num_case++) {
run_case();
}
return 0;
}
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