#include <bits/stdc++.h>
typedef long long ll;
#define pb push_back
#define MS(x,y) memset((x),(y),sizeof((x)))
#define MN 1000000001
using namespace std;
const int nsize = 100001;
int n,m,q;
int parent[nsize];
int sajz[nsize];
vector<int> pat[nsize];
bool vis[nsize];
int vred[nsize];
void dfsConst(int pos, int parnt) {
if (vis[pos]) return;
vis[pos] = true;
parent[pos] = parnt;
for (auto it:pat[pos]) dfsConst(it,pos);
}
bool custComp(int a, int b) {
if (sajz[a] == sajz[b]) return a < b;
return sajz[a] > sajz[b];
}
int res = 1;
void dfs(int pos) {
vector<int> deca;
int bris = pat[pos].size()-1;
for (auto it:pat[pos]) {
if (it == parent[pos]) continue;
dfs(it);
deca.pb(sajz[it]);
}
sort(deca.begin(),deca.end());
for (auto it:deca) {
if (sajz[pos]+it <= q) {
sajz[pos] += it;
bris--;
} else {
res += bris;
return;
}
}
}
int main()
{
#if LOCAL_DEBUG
fstream cin("in.txt");
#endif
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
cin>>n>>q;
m = n-1;
for (int i = 0; i<n; i++) cin>>vred[i];
for (int i = 0; i<m; i++) {
int a,b;
cin>>a>>b;
a--; b--;
pat[a].pb(b);
pat[b].pb(a);
}
MS(vis,0);
for (int i = 0; i<n; i++) sajz[i] = vred[i];
dfsConst(0,0);
dfs(0);
cout<<res<<endl;
}
