//Author RufatM
#include <bits/stdc++.h>
using namespace std;
#define MOD 1000000007
#define INF 1e9+7
#define ll long long
#define ull unsigned long long
#define vi vector<int>
#define vii vector<vector<int>>
#define mii map<int, int>
#define pb push_back
#define pii pair<ll, int>
#define all(a) a.begin(), a.end()
#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
vi adj[100001];
ll dp[100001], value[100001];
ll limit;
int res;
void dfs(int node, int parent) {
dp[node] = value[node];
vi subTree;
for (int child : adj[node]) {
if (child != parent) {
dfs(child, node);
dp[node] += dp[child];
subTree.pb(dp[child]);
}
}
sort(all(subTree), greater<int>());
int idx = 0;
while (dp[node] > limit) {
res++;
dp[node] -= subTree[idx++];
}
}
signed main() {
int t=1;
//cin >> t;
while(t--){
fastio;
int n;
cin >> n >> limit;
for (int i = 1; i <= n; ++i) cin >> value[i];
for (int i = 0; i < n - 1; ++i) {
int u, v;
cin >> u >> v;
adj[u].pb(v);
adj[v].pb(u);
}
dfs(1, 0);
cout << res << '\n';
}
}
