/*
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimize("unroll-loops")
*/
// lethal option
#include<bits/stdc++.h>
using namespace std;
#define all(flg) flg.begin(), flg.end()
#define int long long
#define pb push_back
#define fi first
#define se second
#define endl "\n"
#define eb emplace_back
#define ii pair<int, int>
#define vi vector<int>
#define PI 3.141592653589793238462643383279502884
#define ll long long
#define ld long double
#define for1(i, ff, gg) for(int i = ff; i <= gg; ++i)
#define for2(i, ff, gg) for(int i = ff; i >= gg; --i)
const ll mod = 1e9 + 7;
const int maxN = 300005;
const ll oo = 1e18 + 7;
int n, a[maxN];
int x, y, z, k;
int ans = 0;
vector<int> vc[maxN];
int dfs(int node, int par){
vector<int> eli;
int sum = a[node];
for(int cc : vc[node]) if(cc != par){
eli.pb(dfs(cc, node));
}
sort(all(eli));
for(int cc : eli) sum += cc;
while(sum > k){
sum -= eli.back(); eli.pop_back();
++ans;
}
return sum;
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(NULL);
cout.tie(NULL);
cin >> n >> k;
for1(i, 1, n) cin >> a[i];
for1(i, 2, n){
cin >> x >> y;
vc[x].pb(y);
vc[y].pb(x);
}
dfs(1, 0);
cout << ans << endl;
}
