#include <bits/stdc++.h>
#define Optimize ios_base::sync_with_stdio(false); cin.tie(0);
#define F first
#define S second
#define mp(a, b) make_pair(a, b)
#define iter(a) a.begin(), a.end()
#define ariter(_a, _n) _a, _a+_n
#define dbg(a, b) cout << "var " << a << " -> " << b << '\n';
#define dbg_itv(l, r, val) cout << "### (" << l << ", " << r << ") -> " << val << '\n';
#define flag(_a) cout << "Still alive at flag " << _a << '\n';
#define printv(_a) for (auto& _i : _a) cout << _i << ' '; cout << '\n';
#define printchar(_c, _n) for (int i = 0; i < _n; i++) cout << _c;
#define clear_stk(_s) while (!_s.empty()) _s.pop();
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
const int maxn = 1e5 + 1;
const int lgmx = 17;
const int INF = 2147483647;
const ll LLINF = 1e18;
const int MOD = 1e9 + 7;
int n, k, ans = 0;
vector<int> G[maxn], val;
int dfs(int u, int pa) {
int sz = val[u];
priority_queue<int> kids;
for (auto& i : G[u]) {
if (i == pa) continue;
int kid = dfs(i, u);
sz += kid;
kids.push(kid);
}
while (!kids.empty() && sz > k) {
sz -= kids.top();
ans++;
kids.pop();
}
return sz;
}
int main() {
Optimize
cin >> n >> k;
val.resize(n);
fill(ariter(G, maxn), vector<int>());
for (auto& i : val) cin >> i;
for (int i = 0; i < n-1; i++) {
int u, v; cin >> u >> v;
u--; v--;
G[u].emplace_back(v);
G[v].emplace_back(u);
}
dfs(0, -1);
cout << ans << '\n';
return 0;
}
