#include <bits/stdc++.h>
#define ll long long int
#define mp make_pair
#define pb push_back
#define ld long double
#define pii pair<int,int>
#define sz(x) (int)x.size()
#define piii pair<pii,pii>
#define precise cout<<fixed<<setprecision(10)
#define st first
#define nd second
#define ins insert
#define vi vector<int>
#define BOOST ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0)
using namespace std;
const int MAX=2e5+5;
const int inf=1e9+9;
vector<pii>P[MAX];
int gle[MAX];
int dist[MAX];
int ans=inf;
void brut(int u,int fa,int k)
{
if (fa==-1)gle[u]=0,dist[u]=0;
if (dist[u]==k)ans=min(ans,gle[u]);
for (auto it:P[u])
{
if (it.st!=fa)
{
gle[it.st]=gle[u]+1;
dist[it.st]=dist[u]+it.nd;
brut(it.st,u,k);
}
}
}
void func(int n,int k)
{
for (int i=1;i<=n;i++)brut(i,-1,k);
}
int best_path(int n,int k,int h[][2],int l[])
{
for (int i=0;i<n-1;i++)
P[h[i][0]].pb(mp(h[i][1],l[i])),P[h[i][1]].pb(mp(h[i][0],l[i]));
func(n,k);
if (ans==inf)ans=-1;
return ans;
}
