#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define X first
#define Y second
typedef long long ll;
const int MAXN = 3e6 + 5;
int n, k;
ll ljutina[MAXN];
vector <int> veze[MAXN];
ll suma[MAXN];
int rezovi(int x, int px) {
int koliko = 0;
vector <ll> dodani;
for (auto nx : veze[x]) {
if (nx == px) continue;
koliko += rezovi(nx, x);
suma[x] += suma[nx];
dodani.push_back(suma[nx]);
}
suma[x] += ljutina[x];
if (suma[x] <= k) return koliko;
sort(dodani.begin(), dodani.end());
reverse(dodani.begin(), dodani.end());
while (suma[x] > k) {
suma[x] -= dodani[0];
dodani.erase(dodani.begin());
koliko++;
}
return koliko;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
cin >> n >> k;
for (int i = 0; i < n; i++) cin >> ljutina[i];
int a, b;
for (int i = 1; i < n; i++) {
cin >> a >> b;
--a; --b;
veze[a].pb(b);
veze[b].pb(a);
}
cout << rezovi(0, -1) << '\n';
return 0;
}
