#include <bits/stdc++.h>
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
#define in(x) freopen(x, "r", stdin)
#define out(x) freopen(x, "w", stdout)
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize("-O3")
#define F first
#define S second
#define pb push_back
#define N +1000500
#define M ll(1e9 + 7)
#define sz(x) (int)x.size()
#define re return
#define oo ll(1e9)
#define el '\n'
#define pii pair <int, int>
#define err ld(1e-9)
#define last(x) x.back()
#define all(x) (x.begin(), x.end())
using namespace std;
//using namespace __gnu_pbds;
//typedef tree <int, null_type, less_equal <int> , rb_tree_tag, tree_order_statistics_node_update> ordered_set;
typedef long long ll;
typedef long double ld;
vector <int> vec[N], g[N];
ll f[N], cost[N], k;
int i, n, u, v, ans;
bool cmp(int u, int v)
{
return cost[u] < cost[v];
}
void dfs(int v, int pr)
{
f[v] = cost[v];
vec[v].clear();
for (auto u : g[v])
{
if (u == pr) continue;
dfs(u, v);
f[v] += f[u];
}
if (f[v] > k)
{
sort(g[v].begin(), g[v].end(), cmp);
while (f[v] > k)
{
f[v] -= f[g[v].back()];
g[v].pop_back();
ans++;
}
}
}
int main()
{
srand(time(0));
ios_base::sync_with_stdio(0);
iostream::sync_with_stdio(0);
ios::sync_with_stdio(0);
cin.tie(NULL);
cout.tie(NULL);
// in("input.txt");
// out("output.txt");
cin >> n >> k;
for (i = 1; i <= n; i++) cin >> cost[i];
for (i = 1; i < n; i++)
{
cin >> u >> v;
g[u].pb(v);
g[v].pb(u);
}
dfs(1, -1);
cout << ans;
}
//
//00000
//00110
//00111
//00011
//00000
