#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
typedef long long ll;
ll n, k, h[100005], kolko[100005];
vector <int> ms[100005];
bool cmp(ll x, ll y){
return x > y;
}
ll dfs(int x, int p){
vector <int> v;
kolko[x] = 1;
for(vector <int>::iterator i = ms[x].begin() ; i != ms[x].end() ; ++i){
int o = *i;
if(o == p)
continue;
v.push_back(dfs(o, x));
kolko[x] += kolko[o];
}
sort(v.begin(), v.end(), cmp);
//cout << x << ":" << kolko[x] << endl;
if(!v.empty() && v[0] >= h[x]){
v[0] -= h[x];
kolko[x]--;
int i = 1;
while(i < (int)v.size() && v[0] >= (k - v[i])){
v[0] -= (k - v[i]);
i++;
kolko[x]--;
}
//cout << x << "-" << kolko[x] << endl;
return v[0];
}
//cout << x << "-" << kolko[x] << endl;
return k - h[x];
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
cin >> n >> k;
for(int i = 1 ; i <= n ; ++i){
cin >> h[i];
}
for(int i = 0 ; i < n - 1 ; ++i){
int x, y;
cin >> x >> y;
ms[x].push_back(y);
ms[y].push_back(x);
}
dfs(1, -1);
cout << kolko[1] - 1 << endl;
return 0;
}
