#include <bits/stdc++.h>
#define ll long long
using namespace std;
#define f first
#define s second
#define pb push_back
#define ep emplace
#define eb emplace_back
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define uniquev(v) sort(all(v)), (v).resize(unique(all(v)) - (v).begin())
#define mem(f,x) memset(f , x , sizeof(f))
#define sz(x) (int)(x).size()
#define __lcm(a, b) (1ll * ((a) / __gcd((a), (b))) * (b))
#define mxx *max_element
#define mnn *min_element
#define cntbit(x) __builtin_popcountll(x)
#define len(x) (int)(x.length())
const int N = 1e6 + 10;
vector <pair <int, int>> ed[N];
ll d1[N], d2[N], k;
ll ans = 1e9;
map <ll, int> mp[N];
// x + y - 2 * v = k
// x + y = k + 2 * v
void dfs(int u, int v) {
mp[u][d1[u]] = d2[u];
ll tot = k + 2 * d1[u];
for (auto x : ed[u]) {
if (x.f == v)
continue;
d2[x.f] = d2[u] + 1;
d1[x.f] = d1[u] + x.s;
dfs(x.f, u);
if (sz(mp[u]) < sz(mp[x.f])) {
swap(mp[u], mp[x.f]);
}
for (auto el : mp[x.f]) {
auto it = mp[u].find(tot - el.f);
if (it != mp[u].end()) {
ans = min(ans, it -> s + el.s - d2[u] * 2);
}
}
for (auto el : mp[x.f]) {
if (mp[u].find(el.f) != mp[u].end()) {
mp[u][el.f] = min(mp[u][el.f], el.s);
} else {
mp[u][el.f] = el.s;
}
}
}
}
int best_path(int n, int len, int H[][2], int L[]) {
k = len;
for (int i = 0; i < n - 1; i++) {
ed[H[i][0]].pb({H[i][1], L[i]});
ed[H[i][1]].pb({H[i][0], L[i]});
}
dfs(0, 0);
if (ans > n)
ans = -1;
return ans;
}
