#define _CRT_SECURE_NO_WARNINGS
#include <bits/stdc++.h>
//#include <ext/pb_ds/tree_policy.hpp>
//#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
//using namespace __gnu_pbds;
#define FOR(i,start,end) for(int i=start;i<(int)(end);i++)
#define FORE(i,start,end) for(int i=start;i<=(int)end;i++)
#define RFOR(i,start,end) for(int i = start; i>end; i--)
#define RFORE(i,start,end) for(int i = start; i>=end; i--)
#define all(a) a.begin(), a.end()
#define mt make_tuple
#define mp make_pair
#define v vector
#define sf scanf
#define pf printf
#define dvar(x) cout << #x << " := " << x << "\n"
#define darr(x,n) FOR(i,0,n) cout << #x << "[" << i << "]" << " := " << x[i] << "\n"
typedef long long ll;
typedef long double ld;
typedef pair<int, int > pii;
typedef pair<ll, ll> pll;
//template <class T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<class T> void minn(T &a, T b) { a = min(a, b); }
template<class T> void maxx(T &a, T b) { a = max(a, b); }
void io() {
#ifdef LOCAL_PROJECT
freopen("input.in", "r", stdin); freopen("output.out", "w", stdout);
#else
/* online submission */
#endif
ios_base::sync_with_stdio(false); cin.tie(NULL);
}
const ll MOD = 1000000007LL;
const ll PRIME = 105943LL;
const ll INF = 1e18;
/****************************COI 2018 P1-Paprike*******************************/
const int MAXN = 1e5 + 99;
int N, K;
int H[MAXN];
v<int> adj[MAXN];
int cuts = 0;
int go(int x, int p) {
v<int> chi;
for (auto c : adj[x]) if (c != p)
chi.push_back(go(c, x));
sort(all(chi));
int cur = H[x], i = -1;
while (i + 1<chi.size() && cur + chi[i + 1] <= K) cur += chi[++i];
cuts += chi.size() - 1 - i;
return cur;
}
int main() {
io();
cin >> N >> K;
FORE(i, 1, N) cin >> H[i];
FOR(i, 0, N - 1) {
int a, b;
cin >> a >> b;
adj[a].push_back(b), adj[b].push_back(a);
}
go(1, -1);
cout << cuts << "\n";
return 0;
}
