#include <bits/stdc++.h>
using namespace std;
#define rep(i,s,e) for (ll i = s; i <= e; ++i)
#define rrep(i,s,e) for (ll i = s; i >= e; --i)
#define pb push_back
#define fi first
#define se second
typedef long long ll;
typedef pair<ll, ll> ii;
typedef vector<ll> vi;
typedef vector<ii> vii;
const ll mxn = 3e5;
ll ans = LLONG_MAX, dep[mxn], hdep[mxn], sz[mxn], bot[mxn], k;
vii neibs[mxn];
map<ll, ll> deep[mxn];
map<ll, bool> been[mxn];
void get_depth (ll u, ll prev) {
//cout << u << endl;
sz[u] = 1;
for (ii vd : neibs[u]) {
ll v = vd.fi, d = vd.se;
if (v == prev) continue;
dep[v] = dep[u]+d;
hdep[v] = hdep[u]+1;
get_depth (v, u);
sz[u] += sz[v];
}
}
void dfs (ll u, ll prev) {
//cout << u << endl;
ll heavy = -1, ma = 0;
for (ii vd : neibs[u]) {
ll v = vd.fi;
if (v == prev) continue;
dfs (v, u);
if (sz[v] > ma) {
ma = sz[v];
heavy = v;
}
}
if (heavy==-1) {
bot[u] = u;
deep[u][dep[u]] = hdep[u];
been[u][dep[u]] = 1;
return;
}
bot[u] = bot[heavy];
for (ii vd : neibs[u]) {
ll v = vd.fi;
if (v == prev || v == heavy) continue;
for (ii deps : deep[bot[v]]) {
ll real_dep = deps.fi, high_dep = deps.se;
ll need_dep = k+2*dep[u]-real_dep;
//cout << ans << endl;
if (been[bot[u]][need_dep]) ans = min(ans, high_dep+deep[bot[u]][need_dep]-2*hdep[u]);
//cout << ans << " " << u << "\n";
}
for (ii deps : deep[bot[v]]) {
ll real_dep = deps.fi, high_dep = deps.se;
if (!been[bot[u]][real_dep] || high_dep < deep[bot[u]][real_dep]) {
deep[bot[u]][real_dep] = high_dep;
been[bot[u]][real_dep] = 1;
}
}
}
ll need_dep = k+dep[u];
if (been[bot[u]][need_dep]) ans = min(ans, deep[bot[u]][need_dep]-hdep[u]);
if (!been[bot[u]][dep[u]] || hdep[u] < deep[bot[u]][dep[u]]) {
deep[bot[u]][dep[u]] = hdep[u];
been[bot[u]][dep[u]] = 1;
}
}
int best_path (int n, int ok, int h[][2], int l[]) {
k = ok;
rep (i,0,n-2) {
ll a = h[i][0], b = h[i][1], c = l[i];
neibs[a].pb({b,c}), neibs[b].pb({a,c});
}
get_depth(0,-1);
//cout << "got depth!" << endl;
dfs (0, -1);
return (ans==LLONG_MAX?-1:ans);
}
//int main() {
// ios::sync_with_stdio(0);
// cin.tie(0);
//first test case
// int a1[3][2] = {{0,1},{1,2},{1,3}};
// int b1[3] = {1,2,4};
//
// cout << best_path (4, 3, a1, b1) << "\n";
// cout << "first done" << endl;
//
// //second test case
//
// int a2[2][2] = {{0,1},{1,2}};
// int b2[2] = {1,1};
//
// cout << best_path (3, 3, a2, b2) << "\n";
// cout << "second done" << endl;
//
// //third test case
//
// int a3[10][2] = {{0,1},{0,2},{2,3},{3,4},{4,5},{0,6},{6,7},{6,8},{8,9},{8,10}};
// int b3[10] = {3,4,5,4,6,3,2,5,6,7};
//
// cout << best_path (11, 12, a3, b3) << "\n";
// cout << "thrird done" << endl;
//
//custom one test case
// int ac1[3][2] = {{0,1},{1,2},{2,3}};
// int bc1[3] = {5,5,5};
//
// cout << best_path (3,15,ac1,bc1) << "\n";
//
// return 0;
//}
