#include <bits/stdc++.h>
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
//#pragma GCC optimize("unroll-loops")
//#pragma GCC optimize("-O3")
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("fast-math")
//#pragma GCC optimize("no-stack-protector")
#define F first
#define S second
#define sz(x) int(x.size())
#define pb push_back
#define N 101001
#define M ll(998244353)
#define inf 1e9 + 1e9
using namespace std;
//using namespace __gnu_pbds;
typedef long double ld;
typedef long long ll;
typedef short int si;
typedef array <int, 3> a3;
//typedef tree <int, null_type, less_equal<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
int n, k, a[N], ans, f[N];
vector <int> g[N];
void dfs(int v, int p)
{
f[v] = a[v];
vector <int> gr; gr.clear();
for (auto it : g[v])
{
if (it == p) continue;
dfs(it, v);
gr.pb(f[it]);
}
sort(gr.begin(), gr.end());
for (auto it : gr)
{
if (f[v] + it > k) ans++;
else f[v] += it;
}
}
int main()
{
//freopen("input.txt", "r", stdin); //freopen("output4.txt", "w", stdout);
ios_base::sync_with_stdio(0); istream::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n >> k;
for (int i = 1; i <= n; i++) cin >> a[i];
for (int i = 1; i < n; i++)
{
int x, y;
cin >> x >> y;
g[x].pb(y);
g[y].pb(x);
}
dfs(1, -1);
cout << ans << endl;
}
