#include <cstdio>
#include <stdio.h>
#include <stdbool.h>
#include <iostream>
#include <map>
#include <vector>
#include <climits>
#include <stack>
#include <string>
#include <queue>
#include <algorithm>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <cmath>
#include <cctype>
#include <bitset>
#include <iomanip>
#include <cstring>
#include <numeric>
#include <cassert>
using namespace std;
#define int long long
#define pii pair<int, int>
#define mp make_pair
#define pb push_back
#define fi first
#define se second
int n, k;
vector<int> vect, dp;
vector<vector<int> > graph;
void dfs(int node, int par){
vector<pii> temp;
for (auto num:graph[node])if (num!=par){
dfs(num, node);
dp[node]+=dp[num];
temp.pb(mp(vect[num], num));
}
sort(temp.begin(), temp.end());
for (auto c:temp){
if (vect[node]+c.fi<=k)vect[node]+=c.fi;
else ++dp[node];
}
}
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin>>n>>k;
vect.resize(n+1);
dp.resize(n+1, 0);
graph.resize(n+1);
for (int i=1; i<=n; ++i)cin>>vect[i];
for (int i=1, a, b; i<n; ++i){
cin>>a>>b;
graph[a].pb(b);
graph[b].pb(a);
}
dfs(1, 1);
cout<<dp[1];
}
