//#define NDEBUG
#include <bits/stdc++.h>
#include <bits/extc++.h>
#define StarBurstStream ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define iter(a) a.begin(), a.end()
#define riter(a) a.rbegin(), a.rend()
#define lsort(a) sort(iter(a))
#define gsort(a) sort(riter(a))
#define mp(a, b) make_pair(a, b)
#define pb(a) push_back(a)
#define eb(a) emplace_back(a)
#define pf(a) push_front(a)
#define pob pop_back()
#define pof pop_front()
#define F first
#define S second
#define printv(a, b) {bool pvaspace=false; \
for(auto pva : a){ \
if(pvaspace) b << " "; pvaspace=true;\
b << pva;\
}\
b << "\n";}
#define pii pair<int, int>
#define pll pair<ll, ll>
#define tiii tuple<int, int, int>
#define mt make_tuple
#define gt(t, i) get<i>(t)
#define iceil(a, b) ((a) / (b) + !!((a) % (b)))
//#define TEST
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
using namespace __gnu_pbds;
const ll MOD = 1000000007;
const ll MAX = 2147483647;
template<typename A, typename B>
ostream& operator<<(ostream& o, pair<A, B> p){
return o << '(' << p.F << ',' << p.S << ')';
}
vector<vector<int>> g;
vector<int> h;
vector<int> dp;
int ans = 0;
int n, k;
void dfs(int now, int p){
dp[now] = h[now];
vector<int> t;
for(int i : g[now]){
if(i == p) continue;
dfs(i, now);
t.eb(dp[i]);
}
gsort(t);
while(!t.empty() && dp[now] + t.back() <= k){
dp[now] += t.back();
t.pob;
}
ans += t.size();
}
int main(){
StarBurstStream
cin >> n >> k;
g.resize(n + 1);
h.resize(n + 1);
for(int i = 1; i <= n; i++) cin >> h[i];
for(int i = 1; i < n; i++){
int u, v;
cin >> u >> v;
g[u].eb(v);
g[v].eb(u);
}
dp.resize(n + 1);
dfs(1, 1);
cout << ans << "\n";
return 0;
}
