//The Rumbling starts here:
#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math")
//#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#include<bits/stdc++.h>
using namespace std;
#define debug(n,m) cout<<"["<<#n<<"]->"<<n<<m
#define int long long
#define all(x) x.begin(),x.end()
#define ai array<int,2>
#define vv vector
#define pb push_back
const int N=1e6+5;
const int mod=1e9+7;
const int inf=(1ll<<55)-1;
int n,k;
int a[N];
vector<int> g[N];
int res[N];
void dfs(int u,int p) {
multiset<int> ve;
for (int v : g[u]) {
if (v!=p) {
dfs(v,u);
ve.insert(a[v]);
res[u]+=res[v];
}
}
int d=0;
for (int el : ve) {
if (el+a[u]<=k) {
a[u]+=el;
}
else {
d++;
}
}
res[u]+=d;
}
void levi() {
cin>>n>>k;
for (int i=1;i<=n;++i) cin>>a[i];
for (int i=1;i<=n-1;++i) {
int u,v;
cin>>u>>v;
g[u].pb(v);
g[v].pb(u);
}
dfs(1,0);
cout<<res[1];
}
int32_t main() {
// freopen("bbreeds.in","r",stdin);
// freopen("bbreeds.out","w",stdout);
ios_base::sync_with_stdio(0);
cin.tie(0);
int tt=1;
#ifdef tests
cin>>tt;
#endif
while(tt--) levi();
}
