#include <bits/stdc++.h>
///#define int long long
#define endl '\n'
#define fi first
#define se second
#define mp make_pair
#define pll pair<long long, long long>
#define mein ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
using namespace std;
vector<int>x[100001];
long long dp[100001], val[100001];
long long k;
int ans;
void dfs(int n, int f){
dp[n] = val[n];
vector<int> v;
for(int res: x[n]){
if(res != f){
dfs(res,n);
dp[n] += dp[res];
v.push_back(dp[res]);
}
}
sort(v.begin(), v.end());
reverse(v.begin(), v.end());
int ix = 0;
while(dp[n] > k){
ans++;
dp[n] -=v[ix];
ix++;
}
}
int main() {
mein;
int n;
cin >> n >> k;
for(int i = 1; i <= n; ++i){
cin >> val[i];
}
for(int i = 0; i < n - 1; ++i){
int a,b;
cin >> a >> b;
x[a].push_back(b);
x[b].push_back(a);
}
dfs(1,0);
cout << ans;
}
