// #pragma GCC optimize("O3,unroll-loops")
// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define vi vector<int>
#define vl vector<ll>
#define vii vector<pii>
#define db long double
#define vll vector<pll>
#define endl '\n'
#define all(x) x.begin(), x.end()
#define fastio ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define int long long
const int sz = 1e5 + 5;
int n, k, x, y, res, a[sz], dp[sz];
vi g[sz];
void dfs(int node, int par){
dp[node] = a[node];
vi v;
for(int i : g[node]){
if(i == par) continue;
dfs(i, node);
dp[node] += dp[i];
v.push_back(dp[i]);
}
sort(all(v));
while(dp[node] > k){
// cout << dp[node] << endl;
dp[node] -= v.back();
v.pop_back();
res++;
}
}
void fmain(){
cin >> n >> k;
for(int i = 1; i <= n; i++){
cin >> a[i];
}
for(int i = 1; i < n; i++){
cin >> x >> y;
g[x].push_back(y);
g[y].push_back(x);
}
dfs(1, 1);
cout << res;
}
signed main(){
int tmr = 1;
// cin >> tmr;
while(tmr--){
fmain();
}
}
