// Never let them see you bleed...
#include<bits/stdc++.h>
#define F first
#define S second
#define PB push_back
#define sz(s) int((s).size())
#define bit(n,k) (((n)>>(k))&1)
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
const int maxn = 3e5 + 10, mod = 1e9 + 7, inf = 1e9 + 10;
int a[maxn], n, k, ans;
vector<int> v[maxn];
int dfs(int u, int par = -1){
int sum = a[u];
vector<int> vec;
for(int y : v[u]){
if(y != par){
vec.PB(dfs(y, u));
sum+= vec.back();
}
}
if(sum <= k)
return sum;
sort(vec.begin(), vec.end());
while(sum > k){
ans++;
sum-= vec.back();
vec.pop_back();
}
return sum;
}
int main(){
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie();
cin >> n >> k;
for(int i = 1; i <= n; i++){
cin >> a[i];
}
for(int i = 1; i <= n-1; i++){
int a, b;
cin >> a >> b;
v[a].PB(b);
v[b].PB(a);
}
dfs(1);
return cout << ans << endl, 0;
}
