#include <bits/stdc++.h>
using namespace std;
#define rep(i, l, r) for (int i = (l); i < (r); ++i)
#define per(i, l, r) for (int i = (r - 1); i >= l; --i)
#define ALL(x) (x).begin(), (x).end()
using i64 = long long;
void main_() {
int N;
i64 K;
cin >> N >> K;
vector<i64> H(N);
for (auto &e : H) cin >> e;
vector<vector<int>> Tree(N);
rep(i, 0, N - 1) {
int a, b;
cin >> a >> b;
--a, --b;
Tree[a].push_back(b);
Tree[b].push_back(a);
}
int ans = 0;
auto dfs = [&](auto &&self, const int v, const int p) -> i64 {
vector<i64> res;
for (const auto t : Tree[v]) {
if (t == p) continue;
res.push_back(self(self, t, v));
}
sort(ALL(res));
bool isOk = true;
i64 s = 0;
for (const auto e : res) {
if (isOk and s + e + H[v] <= K) {
s += e;
} else {
isOk = false;
++ans;
}
}
return s + H[v];
};
dfs(dfs, 0, -1);
cout << ans << endl;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
main_();
}
