#include<bits/stdc++.h>
using namespace std;
void DBG() { cerr << "]\n"; }
template<class H, class... T> void DBG(H h, T... t) {
cerr << h; if(sizeof...(t)) cerr << ", ";
DBG(t...);
}
#ifdef LOCAL
#define dbg(...) cerr << "[" << #__VA_ARGS__ << "]: [", DBG(__VA_ARGS__)
#else
#define dbg(...) 0
#endif // LOCAL
#define FOR(i,a,b) for(int i = (a) ; i<(b) ; i++)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for(int i = (b)-1 ; i>=(a) ; i--)
#define R0F(i,a) ROF(i,0,a)
#define each(e,a) for(auto &e : (a))
#define sz(v) (int)(v).size()
#define all(v) (v).begin(),(v).end()
#define rall(v) (v).rbegin(),(v).rend()
#define pb push_back
#define tcT template<class T
#define nl "\n"
#define fi first
#define se second
using ll = long long;
using vi = vector<int>;
using pi = pair<int,int>;
using str = string;
tcT> using V = vector<T>;
tcT> using pqg = priority_queue<T,vector<T>,greater<T>>;
void setIO(string NAME = "") {
cin.tie(0)->sync_with_stdio(0);
if(sz(NAME)) {
freopen((NAME + ".inp").c_str(),"r",stdin);
freopen((NAME + ".out").c_str(),"w",stdout);
}
}
tcT> bool ckmin(T&a, const T&b) {
return b < a ? a=b,1 : 0; }
tcT> bool ckmax(T&a, const T&b) {
return b > a ? a=b,1 : 0; }
const int MOD = 1e9 + 7;
const int MX = 2e5+5;
const ll INF = 1e18;
int N, dep[MX];
V<pi> adj[MX];
map<ll, int> mn_dep[MX];
ll dist[MX], K;
int ans = MOD;
void dfs(int u, int p) {
mn_dep[u][dist[u]] = dep[u];
each(ed, adj[u]) if(ed.fi != p) {
dep[ed.fi] = dep[u] + 1;
dist[ed.fi] = dist[u] + ed.se;
dfs(ed.fi, u);
}
}
void dfsCalc(int u, int p) {
each(ed, adj[u]) if(ed.fi != p) {
dfsCalc(ed.fi, u);
int v = ed.fi;
if(sz(mn_dep[u]) < sz(mn_dep[v])) swap(mn_dep[u], mn_dep[v]);
each(val, mn_dep[v]) {
ll du = K + dist[u]*2 - val.fi;
if(mn_dep[u].find(du) != mn_dep[u].end()) ckmin(ans, val.se + mn_dep[u][du] - 2*dep[u]);
}
each(val, mn_dep[v]) {
if(mn_dep[u].find(val.fi) != mn_dep[u].end()) ckmin(mn_dep[u][val.fi], val.se);
else mn_dep[u][val.fi] = val.se;
}
mn_dep[v].clear();
}
}
int best_path(int n, int k, int eds[][2], int cst[]) {
N = n;
K = k;
F0R(i, N-1) {
int u = eds[i][0], v = eds[i][1], w = cst[i];
adj[u].pb({v, w});
adj[v].pb({u, w});
}
dfs(0, -1);
dfsCalc(0, -1);
if(ans >= MOD) ans = -1;
return ans;
}
