/******************************************************************************
Online C++ Compiler.
Code, Compile, Run and Debug C++ program online.
Write your code in this editor and press "Run" button to compile and execute it.
*******************************************************************************/
#include <bits/stdc++.h>
using namespace std;
vector<int> v[100001];
int h[100001];
long long k;
long long cuts = 0;
long long dfs(int u, int p) {
vector<long long> sums;
for (int x : v[u]) {
if (x == p) continue;
long long s = dfs(x, u);
if (s > k) {
cuts++;
} else {
sums.push_back(s);
}
}
sort(sums.begin(), sums.end());
long long sum = h[u];
for (long long i : sums) {
if (sum + i <= k) {
sum += i;
}
else {
cuts++;
}
}
return sum;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n;
cin>>n>>k;
for(int i = 1 ; i <= n ; i++) cin>>h[i];
for(int i = 0 ; i < n-1 ; i++) {
int x, y;
cin>>x>>y;
v[x].push_back(y);
v[y].push_back(x);
}
dfs(1,-1);
cout<<cuts<<endl;
return 0;
}
