#include <bits/stdc++.h>
using namespace std;
#define MAXN 100005
long long a[MAXN];
long long sz[MAXN];
vector <int> g[MAXN];
int n,k;
int ans=0;
void dfs(int v,int p)
{
sz[v]=a[v];
vector <long long> vals;
for(auto x:g[v])
{
if(x!=p)
{
dfs(x,v);
sz[v]+=sz[x];
vals.push_back(sz[x]);
}
}
sort(vals.begin(),vals.end());
auto it = vals.end();
it--;
while(sz[v]>k)
{
sz[v]-=*it;
ans++;
it--;
}
}
int main()
{
ios_base::sync_with_stdio(false);
cin >> n >> k;
for(int i = 1; i <= n; i++)cin >> a[i];
for(int i = 0; i < n-1; i++)
{
int u,v;
cin >> u >> v;
g[u].push_back(v);
g[v].push_back(u);
}
dfs(1,0);
cout << ans;
return 0;
}
