// In the name of God
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define pb push_back
#define S second
#define F first
#define mp make_pair
#define smax(x, y) (x) = max((x), (y))
#define smin(x, y) (x) = min((x), (y))
#define all(x) (x).begin(), (x).end()
#define len(x) ((int)(x).size())
const int maxn = 2e5 + 5, maxk = 1e6 + 5;
const int inf = 1e9 + 7;
ll n, k, ans = inf, sz[maxn], h[maxn], mn[maxk];
vector<pii> adj[maxn];
vector<int> vec;
bool mark[maxn];
void get_sz(int v, int p = -1){
sz[v] = 1;
for(auto [u, w]: adj[v]){
if(u != p && !mark[u]){
get_sz(u, v);
sz[v] += sz[u];
}
}
}
int find(int v, int s, int p = -1){
for(auto [u, w]: adj[v]) if(u != p && !mark[u] && sz[u] * 2 > s) return find(u, s, v);
return v;
}
void dfs(int v, int h1, int h2, int p, bool keep){
if(h2 > k) return;
if(keep){
smin(mn[h2], 1ll * h1);
vec.pb(h2);
}
else smin(ans, h1 + mn[k - h2]);
for(auto [u, w]: adj[v]) if(u != p && !mark[u]) dfs(u, h1 + 1, h2 + w, v, keep);
}
void centroid_decomp(int v = 0){
get_sz(v);
v = find(v, sz[v]);
mn[0] = 0;
for(auto [u, w]: adj[v]){
if(!mark[u]){
dfs(u, 1, w, v, 0);
dfs(u, 1, w, v, 1);
}
}
mn[0] = inf;
for(auto u: vec) mn[u] = inf;
vec.clear();
mark[v] = 1;
for(auto [u, w]: adj[v]) if(!mark[u]) centroid_decomp(u);
}
int best_path(int N, int K, int H[][2], int L[]){
n = N, k = K;
fill(mn, mn + maxk, inf);
for(int i = 0; i < n - 1; i++){
int u = H[i][0], v = H[i][1], w = L[i];
adj[u].pb(mp(v, w));
adj[v].pb(mp(u, w));
}
centroid_decomp();
return (ans >= inf ? -1 : ans);
}
// int32_t main()
// {
// ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
// fill(mn, mn + maxk, inf);
// cin >> n >> k;
// for(int i = 0; i < n - 1; i++){
// int u, v, w; cin >> u >> v >> w;
// adj[u].pb(mp(v, w));
// adj[v].pb(mp(u, w));
// }
// centroid_decomp();
// cout << (ans >= inf ? -1 : ans) << '\n';
// return 0;
// }
