#include <bits/stdc++.h>
#define ff first
#define ss second
#define pb push_back
#define mp make_pair
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<ll, ll> pll;
typedef pair<ull, ull> pull;
typedef pair<int, int> pii;
typedef pair<ld, ld> pld;
int n, k;
int a[3000009];
vector<int> g[3000009];
int ans;
int f(int v, int p){
vector<int> vec;
for(auto u : g[v]){
if(u == p)
continue;
vec.pb(f(u, v));
}
sort(vec.begin(), vec.end());
int cur = a[v];
for(auto u : vec){
if(u + cur > k)
++ans;
else
cur += u;
}
return cur;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
//freopen("in.txt", "r", stdin);
//freopen("out.txt", "w", stdout);
cin >> n >> k;
for(int i = 1; i <= n; ++i)
cin >> a[i];
for(int i = 1; i < n; ++i){
int t1, t2;
cin >> t1 >> t2;
g[t1].pb(t2);
g[t2].pb(t1);
}
f(1, -1);
cout << ans << "\n";
}
