#include<bits/stdc++.h>
#define debug(x) cerr << #x << " " << x << "\n"
#define debugs(x) cerr << #x << " " << x << " "
#pragma GCC optimize("Ofast")
#define int long long
using namespace std;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int range_rng(int l, int r)
{
return uniform_int_distribution<int>(l,r)(rng);
}
struct info
{
int cuts;
int compsize;
};
info dp[100005];
int s[100005];
int k;
vector<int> nodes[100005];
vector<int> nush;
void dfs(int node, int parent)
{
int taieri,compsz;
taieri=0;
compsz=s[node];
for (auto x : nodes[node])
{
if (x!=parent)
{
dfs(x,node);
taieri+=dp[x].cuts;
compsz+=dp[x].compsize;
}
}
nush.clear();
for (auto x : nodes[node])
{
if (x!=parent)
{
nush.push_back(dp[x].compsize);
}
}
if (compsz<=k)
{
dp[node].cuts=taieri;
dp[node].compsize=compsz;
}
else
{
sort(nush.begin(),nush.end());
while(compsz>k)
{
taieri++;
compsz-=nush.back();
nush.pop_back();
}
dp[node].cuts=taieri;
dp[node].compsize=compsz;
}
}
signed main()
{
/*
ifstream fin("arbore.in");
ofstream fout("arbore.out");
*/
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n,i,j,u,v;
cin >> n >> k;
for (i=1;i<=n;i++)
cin >> s[i];
for (i=1;i<=n-1;i++)
{
cin >> u >> v;
nodes[u].push_back(v);
nodes[v].push_back(u);
}
dfs(1,-1);
cout << dp[1].cuts;
return 0;
}
