#include "bits/stdc++.h"
using namespace std;
int l[100010], r[100010];
int h[100010];
int par[100010];
long long cost[100010];
bool use[100010];
const long long inf = 1e15;
int root(int x) {
if(par[x] == x) return x;
return par[x] = root(par[x]);
}
void join(int x, int y) {
x = root(x);
y = root(y);
if(x != y) {
par[x] = y;
cost[y] += cost[x];
}
}
int main(int argc, char const *argv[])
{
int n, k;
cin >> n >> k;
for(int i = 1; i <= n; i++) cin >> h[i];
for(int i = 1; i < n; i++) {
cin >> l[i] >> r[i];
}
for(int i = 1; i <= n; i++) {
cost[i] = h[i];
par[i] = i;
}
int ans = n-1;
for(int x = 1; x < n; x++) {
int opt = -1;
long long least = inf;
for(int i = 1; i < n; i++) {
if(use[i] == false) {
long long c = cost[root(l[i])] + cost[root(r[i])];
if(opt == -1 || least > c) {
least = c;
opt = i;
}
}
}
if(least <= k) {
join(l[opt], r[opt]);
use[opt] = true;
--ans;
} else {
break;
}
}
printf("%d\n", ans);
return 0;
}
