#include "race.h"
#include<bits/stdc++.h>
#define pb push_back
using namespace std;
const int maxn = 2e6 + 10;
int n, k;
vector < pair< int, int > > g[maxn];
int block[maxn], all, half, sz[maxn];
void calc(int beg, int from)
{
//cout << "calc " << beg << " " << from << endl;
sz[beg] = 1;
for (auto &[nb, w]: g[beg])
{
// cout << "nb? " << nb << endl;
if(nb == from || block[nb])continue;
calc(nb, beg);
sz[beg] += sz[nb];
}
}
int find_centroid(int beg, int from)
{
for (auto &[nb, w]: g[beg])
{
if(nb == from || block[nb])continue;
if(sz[nb] > half)return find_centroid(nb, beg);
}
return beg;
}
vector < pair < int, int > > p;
int ans;
int mp[maxn];
vector < int > rem;
void dfs(int beg, int from, int cnt, int w)
{
if(w > k)return;
if(w == k)
{
ans = min(ans, cnt);
return;
}
else
{
int curr = cnt + mp[k - w];
ans = min(ans, curr);
}
p.pb({w, cnt});
for (auto &[nb, ww]: g[beg])
{
if(nb == from || block[nb])continue;
dfs(nb, beg, cnt + 1, w + ww);
}
}
void decompose(int v, int from)
{
// cout << "decomposing "<< v << endl;
calc(v, -1);
all = sz[v];
half = all/2;
int nc = find_centroid(v, -1);
block[nc] = 1;
// cout << all << " " << half << " " << nc << endl;
for (auto x: rem)
mp[x] = n;
rem.clear();
for (auto &[nb, w]: g[nc])
{
if(block[nb])continue;
dfs(nb, -1, 1, w);
for (auto &[value, cnt]: p)
{
if(mp[value] == n)rem.pb(value);
mp[value] = min(mp[value], cnt);
}
p.clear();
}
for (auto &[nb, w]: g[nc])
{
if(block[nb])continue;
decompose(nb, nc);
}
}
int best_path(int N, int K, int H[][2], int L[])
{
n = N;
k = K;
for (int i = 0; i < n-1; ++ i)
{
int u = H[i][0], v = H[i][1], w = L[i];
g[u].pb({v, w});
g[v].pb({u, w});
}
ans = n;
for (int i = 1; i <= 2*k; ++ i)
mp[i] = n;
decompose(1, -1);
if(ans == n)return -1; //cout << ans << endl;
return ans;
}
/**
11 12
0 1 3
0 2 4
2 3 5
3 4 4
4 5 6
0 6 3
6 7 2
6 8 5
8 9 6
8 10 7
2
*/
