/**
____ ____ ____ ____ ____
||a |||t |||o |||d |||o ||
||__|||__|||__|||__|||__||
|/__\|/__\|/__\|/__\|/__\|
**/
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N_MAX = 100000;
int N, K;
int w[N_MAX + 2];
vector <int> adj[N_MAX + 2];
int minCuts[N_MAX + 2];
int minSum[N_MAX + 2];
void dfs (int u, int par = -1) {
minCuts[u] = 0;
minSum[u] = w[u];
vector <int> sums;
for (int v : adj[u]) {
if (v != par) {
dfs(v, u);
minCuts[u] += minCuts[v];
sums.push_back(minSum[v]);
}
}
sort(sums.begin(), sums.end(), greater <int> ());
while (sums.empty() == false && minSum[u] + sums.back() <= K) {
minSum[u] += sums.back();
sums.pop_back();
}
minCuts[u] += (int) sums.size();
}
int main () {
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
cin >> N >> K;
for (int u = 1; u <= N; u++) {
cin >> w[u];
}
for (int i = 1; i <= N - 1; i++) {
int u, v;
cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
dfs(1);
cout << minCuts[1] << "\n";
return 0;
}
