#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define all(v) begin(v), end(v)
#define pi pair<int, int>
#define vi vector<int>
using namespace std;
const int N = 2e5+3;
vector<pair<int,ll>> g[N];
map<ll, int> mp[N];
int res = 1e9;
int n, k;
ll dist[N]; int dep[N];
void pre(int u, int p, int len, int h){
dist[u] = len;
dep[u] = h;
for(auto [v,w]:g[u]){
if(v == p) continue;
pre(v, u, len + w, h+1);
}
}
void dfs(int u, int p){
mp[u][dist[u]] = dep[u];
for(auto [v,w]:g[u]){
if(v == p) continue;
dfs(v, u);
if(mp[u].size() < mp[v].size()) swap(mp[u], mp[v]);
for(auto [x,y]:mp[v]){
if(mp[u].find(k + 2 * dist[u] - x) != mp[u].end())
res = min(res, mp[u][k+2*dist[u] - x] + y - 2*dep[u]);
}
for(auto [x,y]:mp[v]){
if(mp[u].find(x) != mp[u].end()){
mp[u][x] = min(mp[u][x], y);
}
else{
mp[u][x] = y;
}
}
}
}
int best_path(int N, int K, int H[][2], int L[]){
n = N;
k = K;
for(int i = 0; i < N-1; i++){
g[H[i][0]+1].push_back({H[i][1]+1, L[i]});
g[H[i][1]+1].push_back({H[i][0]+1, L[i]});
}
pre(1, 0, 0, 0);
dfs(1, 0);
return (res == 1e9? -1:res);
}
