#pragma GCC optimize("O3")
#include<bits/stdc++.h>
#define ll long long
#define endl "\n"
#define AI ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
using namespace std;
vector<ll>val;
vector<vector<ll>>edge;
vector<ll>check;
ll k,c=0;
ll dfs(ll i)
{
check[i]=1;
ll x=-1;
ll y=-1;
for(ll j:edge[i])
{
if(!check[j])
{
if(x==-1)
x=dfs(j);
else
y=dfs(j);
}
}
x=max(0LL,x);
y=max(0LL,y);
if(x+y+val[i]>k)
{
c++;
if(min(x,y)+val[i]>k)
{
c++;
return val[i];
}
return min(x,y)+val[i];
}
return x+y+val[i];
}
int main()
{
AI
//freopen("input.txt", "r", stdin);
//freopen("output.txt", "w", stdout);
ll n,a,b,i;
cin>>n>>k;
val.resize(n+1);
for(i=1;i<=n;i++)
cin>>val[i];
edge.resize(n+1);
check.resize(n+1,0);
for(i=1;i<n;i++)
{
cin>>a>>b;
edge[a].push_back(b);
edge[b].push_back(a);
}
for(i=1;i<=n;i++)
{
if(!check[i])
dfs(i);
}
cout<<c<<endl;
}
