#include <bits/stdc++.h>
// solved by bekagg
#define ll long long
#define ent '\n'
#define pb push_back
#define all(x) x.begin(),x.end()
#define PRaim_bek_abi ios_base::sync_with_stdio(0);cin.tie(0);
using namespace std;
const int N = 2e5+5;
const int MOD = 1e9+7;
int d[N] , t[N] , ans = INT_MAX , dist;
vector< pair<int , int> >g[N];
map<int,int> mp[N];
void dfs(int v , int p){
mp[v][t[v]] = d[v];
for (auto [to , c] : g[v]){
if (to == p) continue;
d[to] = d[v] + 1;
t[to] = t[v] + c;
dfs(to , v);
if (mp[v].size() < mp[to].size()){
swap(mp[to] , mp[v]);
}
for (auto [too , c] : mp[to]){
if (c == 0 or mp[v][(dist - too + 2 * t[v])] == 0) continue;
ans = min(ans , mp[v][(dist - too + 2 * t[v])] + c - 2 * d[v]);
}
for (auto [too , c] : mp[to]){
if (c == 0) continue;
if (mp[v][too] == 0) mp[v][too] = c;
else mp[v][too] = min(mp[v][too] , c);
}
}
// to2 - d[v] = k - (to1 - d[v])
// to2 - d[v] = k - to1 + d[v]
// to2 = k - to1 + 2 * d[v]
}
int best_path(int n , int k , int h[][2] , int l[]){
dist = k;
for (int i = 0; i < n - 1; i++){
g[h[i][0]].pb({h[i][1] , l[i]});
g[h[i][1]].pb({h[i][0] , l[i]});
}
d[1] = 1;
dfs(1 , 0);
return (ans == INT_MAX ? -1 : ans);
}
