#include <bits/stdc++.h>
#define pb push_back
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define debug(x) cerr << #x << " : " << x << '\n'
using namespace std;
typedef long long ll;
typedef long double ld;
typedef string str;
typedef pair<ll, ll> pll;
const ll Mod = 1000000007LL;
const int N = 1e5 + 10;
const ll Inf = 2242545357980376863LL;
const ll Log = 30;
ll n, k;
ll a[N], dp[N], c[N];
vector<ll> G[N];
bool CMP(int i, int j){
return c[i] < c[j];
}
void DFS(int u, int p){
dp[u] = 0;
c[u] = a[u];
for(auto adj : G[u]){
if(adj == p) continue;
DFS(adj, u);
dp[u] += dp[adj] + 1;
}
sort(all(G[u]), CMP);
for(auto adj : G[u]){
if(adj == p) continue;
if(c[u] + c[adj] <= k){
dp[u] --;
c[u] += c[adj];
}
}
}
int main(){
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n >> k;
for(int i = 1; i <= n; i++) cin >> a[i];
int u, v;
for(int i = 1; i < n; i++){
cin >> u >> v;
G[u].pb(v);
G[v].pb(u);
}
DFS(1, -1);
cout << dp[1] << '\n';
return 0;
}
