#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 100'000 + 10;
int n, k, par[N], c[N];
ll a[N];
vector<int> G[N];
void dfs(int v, int p = 0)
{
par[v] = p;
for(int u : G[v])
if(u != p)
dfs(u, v), c[v]++;
}
int main()
{
cin >> n >> k;
for(int i = 1; i <= n; i++)
cin >> a[i];
for(int i = 1; i < n; i ++)
{
int u, v;
cin >> u >> v;
G[u].push_back(v);
G[v].push_back(u);
}
dfs(1);
int ans = 0;
set<pair<ll,int> > st;
for(int i = 2; i <= n; i ++)
if(c[i] == 0)
st.insert({a[i], i});
while(st.size())
{
int v = st.begin()->second;
st.erase(st.begin());
// cerr << v << ' ' << a[v] << ' ' << par[v] << ' ' << a[par[v]] << endl;
if(a[par[v]] + a[v] <= k)
a[par[v]] += a[v];
else
ans++;
c[par[v]]--;
if(c[par[v]] == 0 && par[v] != 1)
st.insert({a[par[v]], par[v]});
}
cout << ans << endl;
return 0;
}
