#include <bits/stdc++.h>
#ifndef dbg
#define dbg(...)
#endif
#define all(x) begin(x), end(x)
#define rsz(...) resize(__VA_ARGS__)
#define psh(...) push_back(__VA_ARGS__)
#define emp(...) emplace_back(__VA_ARGS__)
#define prt(...) print(cout, __VA_ARGS__)
#define dmp(...) print(cerr, #__VA_ARGS__, '=', __VA_ARGS__)
#define dprt(...) dbg(print(cerr,__VA_ARGS__))
#define ddmp(...) dbg(dmp(__VA_ARGS__))
using namespace std;using ll=long long;
template<typename t>using V=vector<t>;
template<typename t>void print(ostream& os, const t& a){os<<a<<'\n';}
template<typename t, typename... A>void print
(ostream& os, const t& a, A&&... b){os<<a<<' ';print(os, b...);}
int n, k, r;
V< ll > val;
V< V< int > > gr;
inline void dfs (int v, int o)
{
for (int s : gr[v])
if (s != o)
dfs(s, v);
V< int > ilo;
for (int s : gr[v])
if (s != o)
{
val[v] += val[s];
ilo.psh(val[s]);
}
sort(all(ilo));
reverse(all(ilo));
int pt = 0;
while (val[v] > k)
{
val[v] -= ilo[pt++];
++r;
}
}
int main()
{
ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n >> k;
gr.rsz(n + 1);
val.rsz(n + 1);
for (int i = 1; i <= n; ++i)
cin >> val[i];
for (int i = 0; i < n - 1; ++i)
{
int p, q; cin >> p >> q;
gr[p].psh(q);
gr[q].psh(p);
}
dfs(1, 1);
prt(r);
}
