#include "race.h"
#include <bits/stdc++.h>
#define N 200005
#define pb push_back
#define ff first
#define ss second
#define pii pair<int, int>
using namespace std;
bool blocked[N];
int n, s;
vector<pii> adj[N];
int sz[N];
int sumsz;
int len[5 * N];
int get_size(int v, int p){
sz[v] = 1;
for(auto& c : adj[v]){
if(c.ff == p || blocked[c.ff])
continue;
sz[v] += get_size(c.ff, v);
}
return sz[v];
}
int get_centroid(int v, int p){
for(auto& c : adj[v]){
if(c.ff == p || blocked[c.ff])
continue;
if(sz[c.ff] >= sumsz / 2)
return get_centroid(c.ff, v);
}
return v;
}
int ans = N;
queue<pii> q;
queue<int> lol;
void dfs(int v, int p, int l, int cnt){
if(s >= l)ans = min(ans, len[s - l] + cnt);
else return;
q.push({l, cnt});
lol.push(l);
cnt++;
for(auto& c : adj[v]){
if(c.ff == p || blocked[c.ff])
continue;
dfs(c.ff, v, l + c.ss, cnt);
}
if(p == -1){
while(!q.empty()){
len[q.front().ff] = min(len[q.front().ff], q.front().ss);
q.pop();
}
}
}
void decomp(int v){
sumsz = get_size(v, -1);
v = get_centroid(v, -1);
blocked[v] = 1;
len[0] = 0;
for(auto &c : adj[v]){
if(blocked[c.ff])
continue;
dfs(c.ff, -1, c.ss, 1);
}
while(!lol.empty()){
len[lol.front()] = 0x3f3f3f3f;
lol.pop();
}
for(auto &c : adj[v]){
if(blocked[c.ff])
continue;
decomp(c.ff);
}
}
int best_path(int n, int s, int h[][2], int l[]){
::n = n;
::s = s;
memset(len, 0x3f, sizeof len);
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]});
}
decomp(1);
return (ans == N ? -1 : ans);
}
