#include <bits/stdc++.h>
#define int long long
using namespace std;
const int nmax = 100000;
int n, k;
int v[nmax + 5];
struct elem
{
int minCuts;
int minSum;
};
elem dp[nmax + 5];
vector<int> g[nmax + 5];
void dfs(int fiu, int tata)
{
priority_queue<int> coada;
dp[fiu].minCuts = 0;
dp[fiu].minSum = v[fiu];
for(auto it : g[fiu])
{
if(it == tata)
{
continue;
}
dfs(it, fiu);
dp[fiu].minCuts += dp[it].minCuts;
dp[fiu].minSum += dp[it].minSum;
coada.push(dp[it].minSum);
}
while(dp[fiu].minSum > k)
{
dp[fiu].minCuts ++;
dp[fiu].minSum -= coada.top();
coada.pop();
}
}
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n >> k;
for(int i = 1; i <= n; i ++)
{
cin >> v[i];
}
for(int i = 1; i < n; i ++)
{
int u, v;
cin >> u >> v;
g[u].push_back(v);
g[v].push_back(u);
}
dfs(1, 0);
cout << dp[1].minCuts << '\n';
return 0;
}
