#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
int spice[1000006];
int n, k;
vector<int> graph[1000006];
int c = 0;
bool visited[1000006];
ll dp[1000006];
void dfs(int u)
{
//cout << u << " \n";
visited[u] = true;
vector<pair<ll ,int>> children;
dp[u] += spice[u];
for(auto v: graph[u])
{
if(!visited[v])
{
dfs(v);
children.push_back({dp[v], v});
//cout << dp[v] << "l ";
}
}
//cout << '\n';
int cnt = children.size();
sort(children.begin(), children.end());
for(auto p : children)
{
if(dp[u] + p.first > k)
{
//cout << cnt << " and " << c << '\n';
c += cnt;
break;
}
dp[u] += p.first;
cnt --;
}
}
int main()
{
cin >> n >> k;
for(int i = 1; i <= n; i ++)
{
cin >> spice[i];
}
for(int i = 0; i < n-1; i ++)
{
int a, b;
cin >> a >> b;
graph[a].push_back(b);
graph[b].push_back(a);
}
dfs(1);
cout << c;
}
