#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define lb lower_bound
#define ff first
#define ss second
typedef long long ll;
typedef pair<ll, int> ii;
typedef vector<int> vi;
const int maxn = 1e5 + 7;
ll n, k, t = 1, h[maxn], in[maxn], ou[maxn], p[18][maxn], sm[maxn], fw[maxn];
bool ins[maxn];
vi ls[maxn];
set<ii> s;
void dfs(int v){
in[v] = t;
sm[v] = h[v];
t++;
for (int i = 1; i < 18; i++)
p[i][v] = p[i - 1][p[i - 1][v]];
for (int ss : ls[v]){
if (ss == p[0][v]) continue;
p[0][ss] = v;
dfs(ss);
sm[v] += sm[ss];
}
ou[v] = t - 1;
s.insert({-sm[v], v});
}
void upd(int i, ll v){
for (; i < maxn; i += (i & -i))
fw[i] += v;
}
ll qu(int i){
ll ret = 0;
for (; i > 0; i -= (i & -i))
ret += fw[i];
return ret;
}
ll ssum(int v){
return qu(ou[v]) - qu(in[v] - 1);
}
void rem(int v){
if (!ins[v]) return;
ins[v] = 0;
for (int ss : ls[v]){
if (ss == p[0][v]) continue;
rem(ss);
}
}
int main(){
// ios_base::sync_with_stdio(0);
// cin.tie(0); cout.tie(0);
cin >> n >> k;
for (int i = 1; i <= n; i++){
cin >> h[i];
ins[i] = 1;
}
for (int i = 1; i < n; i++){
int x, y;
cin >> x >> y;
ls[x].pb(y);
ls[y].pb(x);
}
p[0][1] = 1;
dfs(1);
for (int i = 1; i <= n; i++)
upd(in[i], h[i]);
ll uk = sm[1], ans = 0;
while(uk > k){
ii njb = *s.lb({-k, 0});
s.erase(s.find(njb));
int v = njb.ss;
ll sb = -njb.ff;
if (!ins[v]){
continue;
}
if (sb != ssum(v)){
continue;
}
ans++;
uk -= sb;
upd(in[v], -sb);
rem(v);
int sv = v;
for (int i = 17; i >= 0; i--){
int nv = p[i][v];
if (ssum(nv) <= k)
v = nv;
}
if (sv != v) s.insert({-ssum(v), v});
}
cout << ans << "\n";
return 0;
}
