#include <bits/stdc++.h>
#include "race.h"
#define startt ios_base::sync_with_stdio(false);cin.tie(0);
typedef long long ll;
using namespace std;
#define vint vector<int>
#define all(v) v.begin(), v.end()
#define MOD 1000000007
#define MOD2 998244353
#define MX 1000000000
#define MXL 1000000000000000000
#define PI (ld)2*acos(0.0)
#define nax 200005
#define pb push_back
#define sc second
#define fr first
//#define int long long
//#define endl '\n'
#define ld long double
#define NO cout << "NO" << endl
#define YES cout << "YES" << endl
vector<pair<int, ll>> adj[200005];
int n_glob;
ll k_glob;
vint size_sub;
vint del;
int calc(int u, int par)
{
int children = 1;
for(auto v : adj[u])
{
if(del[v.fr] == 0 && (par == -1 || v.fr != par))
{
children+=calc(v.fr, u);
}
}
size_sub[u] = children;
return children;
}
int find_centroid(int u, int size, int par)
{
for(auto v : adj[u])
{
if(v.fr != par && del[v.fr] == 0 && size_sub[v.fr] > size)
{
return find_centroid(v.fr, size, u);
}
}
return u;
}
ll ans = MXL;
void assign(int u)
{
size_sub = vint(n_glob+1);
calc(u, -1);
int centroid = find_centroid(u, size_sub[u] / 2, -1);
map<int, ll> cnt;
cnt[0] = 0;
del[centroid] = 1;
for(auto x : adj[centroid])
{
if(del[x.fr] == 1)
{
continue;
}
map<int, ll> now;
queue<pair<pair<int, int>, pair<ll, ll>>> q;
q.push({{x.fr, centroid}, {x.sc, 1}});
while(!q.empty())
{
int node = q.front().fr.fr;
int parent = q.front().fr.sc;
ll length = q.front().sc.fr;
ll highways = q.front().sc.sc;
if(now[length] == 0LL)
{
now[length] = highways;
}
else
{
now[length] = min(now[length], highways);
}
q.pop();
for(auto y : adj[node])
{
if(del[y.fr] == 0 && y.fr != parent && length+y.sc <= k_glob)
{
q.push({{y.fr, node}, {length+y.sc, highways+1}});
}
}
}
for(auto num : now)
{
if(k_glob == num.fr)
{
ans = min(ans, num.sc);
}
if(k_glob > num.fr && cnt[k_glob-num.fr] != 0)
{
ans = min(ans, num.sc+cnt[k_glob-num.fr]);
}
}
for(auto num : now)
{
if(cnt[num.fr] == 0)
{
cnt[num.fr] = num.sc;
}
else
{
cnt[num.fr] = min(cnt[num.fr], num.sc);
}
}
}
for(auto x : adj[u])
{
if(del[x.fr] == 0)
{
assign(x.fr);
}
}
}
int best_path(int n, int k, int h[][2],int l[])
{
ans = MXL;
n_glob = n;
k_glob = k;
for(int i = 0; i <= n; i++)
{
adj[i].clear();
}
for(int i = 0; i < n-1; i++)
{
adj[h[i][0]].pb({h[i][1], l[i]});
adj[h[i][1]].pb({h[i][0], l[i]});
}
size_sub.clear();
del.clear();
size_sub = vint(n+1);
del = vint(n+1);
assign(0);
if(ans == MXL)
{
assert(false);
return -1;
}
return ans;
}
/*
int32_t main(){
startt
int n, k;
cin >> n >> k;
int h[n-1][2], l[n-1];
for(int i = 0; i < n-1; i++)
{
cin >> h[i][0] >> h[i][1];
}
for(int i = 0; i < n-1; i++)
{
cin >> l[i];
}
cout << best_path(n, k, h, l) << endl;
}
*/
/*
3 3
0 1
0 2
1 1
4 3
0 1
1 2
1 3
1 2 4
11 12
0 1
0 2
2 3
3 4
4 5
0 6
6 7
6 8
8 9
8 10
3 4 5 4 6 3 2 5 6 7
*/
