#include <bits/stdc++.h>
#define Loop(x,l,r) for (ll x = (l); x < (ll)(r); ++x)
#define LoopR(x,l,r) for (ll x = (r)-1; x >= (ll)(l); --x)
typedef long long ll;
typedef std::pair<int, int> pii;
typedef std::pair<ll , ll > pll;
using namespace std;
const int N = 100'010;
vector<int> A[N];
ll h[N];
int n; ll k;
pll dfs(int v, int p)
{
int ans = 1;
vector<ll> vec;
for (int u : A[v]) {
if (u != p) {
auto [x, y] = dfs(u, v);
ans += x;
vec.push_back(y);
}
}
sort(vec.begin(), vec.end());
ll sum = h[v];
for (auto x : vec) {
if (sum + x > k)
break;
sum += x;
ans -= 1;
}
return {ans, sum};
}
int main()
{
cin.tie(0) -> sync_with_stdio(false);
cin >> n >> k;
Loop (i,0,n)
cin >> h[i];
Loop (i,1,n) {
int v, u;
cin >> v >> u;
--v; --u;
A[v].push_back(u);
A[u].push_back(v);
}
cout << dfs(0, -1).first - 1 << '\n';
}
