#include <bits/stdc++.h>
using namespace std;
constexpr int N = 2e5 + 1;
vector<pair<int, long long>> a[N];
map<long long, long long> mn[N];
long long ans = LONG_LONG_MAX;
long long dist[N], sum[N];
int n, k;
void dfs(int v, int p){
mn[v][sum[v]] = dist[v];
for (auto [u, w] : a[v]) {
if (u != p) {
sum[u] = sum[v] + w;
dist[u] = dist[v] + 1;
dfs(u, v);
}
}
long long g = k + 2 * sum[v];
for (auto &[u, w] : a[v]) {
if (u != p) {
dfs(u, v);
if (mn[v].size() < mn[u].size()) {
swap(mn[v], mn[u]);
}
for (auto [x, y] : mn[u]) {
if (mn[v].count(g - x)) {
ans = min(ans, y + mn[v][g - x] - 2 * dist[v]);
}
}
for (auto [x, y] : mn[u]) {
if (mn[v].count(x)) {
mn[v][x] = min(mn[v][x], y);
}
else mn[v][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++) {
a[h[i][0]].emplace_back(h[i][1], l[i]);
a[h[i][1]].emplace_back(h[i][0], l[i]);
}
dfs(0, -1);
return (ans == LONG_LONG_MAX ? -1 : ans);
}
