#include<bits/stdc++.h>
using namespace std;
//#pragma gcc optimize("O3,unroll-loop")
//#pragma gcc target("sse,sse2,sse3,ssse3,sse4,avx,avx2,fma,abm,mmx,popcnt,tune=native")
#define int long long
bool vis[100001];
int n, kk, val[100001], dp[100001], ans;
vector<int> edge[100001];
int dfs(int k)
{
vis[k] = true;
vector<int> vs;
dp[k] = val[k];
for (int i : edge[k])
if (!vis[i])
{
int t = dfs(i);
vs.push_back(t), dp[k] += t;
}
sort(vs.begin(), vs.end(), greater<int>());
int t = 0;
while (dp[k] > kk)
dp[k] -= vs[t], t++, ans++;
return dp[k];
}
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cin >> n >> kk;
for (int i = 1; i <= n; i++)
cin >> val[i];
int a, b;
for (int i = 1; i < n; i++)
cin >> a >> b, edge[a].push_back(b), edge[b].push_back(a);
dfs(1);
cout << ans << '\n';
return 0;
}
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