#include <iostream>
#include <string>
#include <queue>
#include <stack>
#include <algorithm>
#include <math.h>
#include <vector>
#include <cstring>
#include <ctime>
#include <set>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <iomanip>
#include <ctime>
#define fr first
#define sc second
#define MP make_pair
#define PB push_back
#define fastio ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define lli long long int
#define y1 arayikhalatyan
using namespace std;
lli gcd(lli a, lli b) {
if (b == 0)
return a;
return gcd(b, a % b);
}
lli cg(lli n) {
return n ^ (n >> 1);
}
lli SUM(lli a)
{
return (a * (a + 1) / 2);
}
bool CAN(int x, int y, int n, int m)
{
if (x >= 0 && y >= 0 && x < n && y < m)
{
return true;
}
return false;
}
double her(double x1, double y1, double x2, double y2)
{
return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}
string strsum(string a, string b)
{
int p = 0;
string c;
reverse(a.begin(), a.end());
reverse(b.begin(), b.end());
if (b.length() < a.length())
{
for (int i = b.length(); i < a.length(); i++)
{
b += "0";
}
}
else
{
for (int i = a.length(); i < b.length(); i++)
{
a += "0";
}
}
a += "0", b += "0";
for (int i = 0; i < a.length(); i++)
{
c += (a[i] - '0' + b[i] - '0' + p) % 10 + '0';
p = (a[i] + b[i] - '0' - '0' + p) / 10;
}
if (c[c.length() - 1] == '0') c.erase(c.length() - 1, 1);
reverse(c.begin(), c.end());
return c;
}
string strmin(string a, string b)
{
if (a.length() > b.length()) return b;
if (b.length() > a.length()) return a;
for (int i = 0; i < a.length(); i++)
{
if (a[i] > b[i]) return b;
if (b[i] > a[i]) return a;
}
return a;
}
char vow[] = { 'a', 'e', 'i', 'o', 'u' };
int dx[] = { 1, -1, 0, 0 };
int dy[] = { 0, 0, 1, -1 };
const int N = 1e6 + 30;
const lli mod = 998244353;
int n, k, pat;
int a[N];
vector <int> g[N];
bool col[N];
lli t[N];
void dfs1(int v)
{
col[v] = true;
for (auto p : g[v])
{
if (!col[p])
{
dfs1(p);
t[v] += t[p];
}
}
t[v] += a[v];
}
void dfs(int v)
{
col[v] = true;
if (t[v] <= k) return;
t[v] = a[v];
priority_queue <int> fp;
for (auto p : g[v])
{
if (!col[p])
{
dfs(p);
t[v] += t[p];
fp.push(t[p]);
}
}
while (t[v] > k)
{
pat++;
t[v] -= fp.top();
fp.pop();
}
}
int main()
{
fastio;
cin >> n >> k;
for (int i = 1; i <= n; i++) cin >> a[i];
for (int i = 0; i < n - 1; i++)
{
int a, b;
cin >> a >> b;
g[a].PB(b);
g[b].PB(a);
}
dfs1(1);
for (int i = 0; i < n; i++) col[i + 1] = false;
dfs(1);
cout << pat;
return 0;
}
