#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
#define mp make_pair
#define pb push_back
#define F first
#define S second
#define debug(x) std::cout << #x << ": " << x << "\n"
#define all(v) v.begin(), v.end()
#define li(i,a,b) for (int (i) = (a); (i) < (b); (i)++)
#define endl '\n'
#define mem(name,val) memset(name,val,sizeof(name))
#define min(a,b) (a<=b ? a : b)
#define max(a,b) (a>=b ? a : b)
//using u64 = uint64_t;
//using u128 = __uint128_t;
const int nmax = 2e5+3;
vector<pii> adj[nmax];
int K, sz[nmax], r[nmax];
ll ans = INT_MAX;
int dfs_sz(int u, int p=-1){
sz[u]=1;
for(auto [v,_]:adj[u]){
if(p==v||r[v])continue;
sz[u]+=dfs_sz(v,u);
}
return sz[u];
}
int get_cent(int u, int ts, int p=-1){
for(auto [v,_] : adj[u]){
if(p==v||r[v])continue;
if(sz[v]*2>ts)return get_cent(v,ts,u);
}
return u;
}
vector<pii> vec;
void slv_cent(int u, int p, int sum, int cnt){
if(sum>K || cnt > ans) return;
vec.pb({sum,cnt});
for(auto [v,len]: adj[u]){
if(p==v || r[v]) continue;
slv_cent(v,u,sum+len,cnt+1);
}
}
void solve(int u){
u = get_cent(u,dfs_sz(u));
r[u]=1;
map<int, int> bes;
for(auto [v,len] : adj[u]){
if(r[v]) continue;
slv_cent(v,u,len,1);
for(auto &p : vec){
if(bes.find(K-p.F) != bes.end()){
ans = min(ans, bes[K-p.F]+p.S);
}
else if(p.F == K){
ans = min(ans, p.S);
}
}
for(auto &p : vec){
if(bes.find(p.F) == bes.end()){
bes[p.F]=p.S;
}
else{
bes[p.F] = min(p.S,bes[p.F]);
}
}
vec.clear();
}
for(auto [v,_] : adj[u]){
if(!r[v]) solve(v);
}
}
int best_path(int n, int k, int h[][2], int l[]){
K=k;
li(i,0,n-1){
adj[h[i][0]].pb({h[i][1],l[i]});
adj[h[i][1]].pb({h[i][0],l[i]});
}
mem(r,0);
solve(0);
return ans==INT_MAX?-1:ans;
}
