#include "race.h"
#include <bits/stdc++.h>
using namespace std;
#define mp make_pair
#define pb push_back
#define len(a) (int)a.size()
#define fi first
#define sc second
#define d1(w) cerr<<#w<<":"<<w<<endl;
#define d2(w,c) cerr<<#w<<":"<<w<<" "<<#c<<":"<<c<<endl;
#define d3(w,c,z) cerr<<#w<<":"<<w<<" "<<#c<<":"<<c<<" "<<#z<<":"<<z<<endl;
#define left isc+isc
#define right isc+isc+1
#define mid (l+r)/2
#define FAfi_IO ios_base::sync_with_fidio(false);
#define escl '\n'
#define bit __builtin_popcount
typedef long long int ll;
const int maxn = 620;
const long long LINF = 1e18;
const int LOG = 31;
const int INF = 1e9;
const int N = 2e5 + 5;
const int M = 1e6 + 5;
const int SQ = 350;
const int MOD = 998244353;
typedef long long int lli;
typedef pair<int,int> pii;
vector <pii> ed[N],vec;
vector <int> v;
int n,k,ans = INF,sub[N],vis[N],mark[M];
int calc(int cur,int back = -1) {
sub[cur] = 0;
for (auto i : ed[cur])
if (i.fi != back && vis[i.fi] == 0)
sub[cur] += calc(i.fi,cur);
return ++sub[cur];
}
int find(int cur,int back,int sz) {
for (auto i : ed[cur])
if (i.fi != back && vis[i.fi] == 0 && sub[i.fi] > sz / 2)
return find(i.fi,cur,sz);
return cur;
}
void dfs(int cur,int back,int sum,int step) {
if (sum == k)
ans = min(ans,step);
if (sum < k) {
ans = min(ans,mark[k - sum] + step);
vec.pb(mp(sum,step));
}
for (auto i : ed[cur]) {
if (vis[i.fi] == 0 && i.fi != back)
dfs(i.fi,cur,sum + i.sc,step + 1);
}
}
void solve(int cur = 1) {
int cen = find(cur,-1,calc(cur));
v.clear();
for (auto i : ed[cen]) {
if (vis[i.fi]) continue;
vec.clear();
dfs(i.fi,cen,i.sc,1);
for (auto j : vec) {
mark[j.fi] = min(mark[j.fi],j.sc);
v.pb(j.fi);
}
}
for (auto i : v)
mark[i] = INF;
vis[cen] = 1;
for (auto i : ed[cen])
if (vis[i.fi] == 0)
solve(i.fi);
}
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] + 1, v = H[i][1] + 1 , c = L[i];
ed[u].pb(mp(v,c));
ed[v].pb(mp(u,c));
}
for (int i = 0 ; i <= k ; i++) mark[i] = INF;
solve();
if (ans >= INF) return -1;
return ans;
}
