#include "race.h"
#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define OVL(v,s) for(auto x:v) cout<<x<<s;cout<<endl;
#define all(v) v.begin(),v.end()
#define F first
#define S second
#define pb push_back
void dbg_out() { cout << endl; }
template<typename Head, typename... Tail> void dbg_out(Head H, Tail... T) { cout << ' ' << H; dbg_out(T...); }
#define dbg(...) cout << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__);
#define endl "\n"
#define mod 1000000007
const ll INF=1e18;
const int MAXN=3000;
ll depth1[MAXN];
ll depth[MAXN];
const int LOGN=17;
int up[MAXN][LOGN];
vector<vector<pair<int,ll>>> v(MAXN);
void dfs(int node,int par,ll ew=0){
depth[node]=depth[par]+ew;
depth1[node]=depth1[par]+1;
up[node][0]=par;
for(int i=1;i<LOGN;i++) up[node][i]=up[up[node][i-1]][i-1];
for(auto x:v[node]) {
if(x.F!=par) dfs(x.F,node,x.S);
}
}
int LCA(int a,int b){
if(depth1[a]<depth[b]) swap(a,b);
int d=depth1[a]-depth1[b];
for(int i=LOGN-1;i>=0;i--){
if((1<<i)&d) a=up[a][i];
}
if(a==b) return a;
for(int i=LOGN-1;i>=0;i--){
if(up[a][i]!=up[b][i]) a=up[a][i],b=up[b][i];
}
return up[a][0];
}
int best_path(int N, int K, int H[][2], int L[])
{
for(int i=0;i<MAXN;i++) depth1[i]=0,depth[i]=0;
for(int i=0;i<N-1;i++){
v[H[i][0]].push_back({H[i][1],L[i]});
v[H[i][1]].push_back({H[i][0],L[i]});
}
dfs(1,1);
ll ans=INF;
for(int i=0;i<N;i++){
for(int j=0;j<N;j++){
if(i^j){
int l=LCA(i,j);
ll dist=depth[i]+depth[j]-(ll)2*depth[l];
if(dist==K){
ans=min(ans,depth1[i]+depth1[j]-(ll)2*depth1[l]);
}
}
}
}
return (ans==INF?-1:ans);
}
#ifdef IOI
#define MAX_N 500000
static int N, K;
static int H[MAX_N][2];
static int L[MAX_N];
static int solution;
inline
void my_assert(int e) {if (!e) abort();}
void read_input()
{
int i;
my_assert(2==scanf("%d %d",&N,&K));
for(i=0; i<N-1; i++)
my_assert(3==scanf("%d %d %d",&H[i][0],&H[i][1],&L[i]));
my_assert(1==scanf("%d",&solution));
}
int main()
{
int ans;
read_input();
ans = best_path(N,K,H,L);
if(ans==solution)
printf("Correct.\n");
else
printf("Incorrect. Returned %d, Expected %d.\n",ans,solution);
return 0;
}
#endif
