#include <iostream>
#include <vector>

#define int long long
#define NMax (int) 1e5+1
using namespace std;

int MIJ;
int k,n;

int f [NMax];
int p [NMax];

vector<pair<int,int> > G[NMax];

int BinarySearch(int lvl)
{

    if(f[lvl] <= MIJ)
        return lvl;

    int in = 1;
    int sf = lvl-1;
    int mij;

    while(in <= sf)
    {
        mij = (in+sf) /2;
        if(f[lvl] - f[mij] <= MIJ)
            in = mij+1;
        else
            sf = mij-1;
    }
    return sf;
}

int Compute(int nod,int lvl)
{
    int c = 0;
    pair<int,int> edge;
    for(int i = 0 ;i<  G[nod].size() ; i++)
    {
        edge = G[nod][i];
        if(edge.first != p[nod])
        {
            p[edge.first] = nod;
            f[lvl] = f[lvl-1] + edge.second;

            c += BinarySearch(lvl);
            c += Compute(edge.first,lvl+1);
        }
    }
    return c;
}

int Search()
{
    int in = 0;
    int sf = 1e15;
    int mij,res  = -1;

    while(in<=sf)
    {
        mij = (in+sf)/2;
        MIJ = mij;
        if( Compute(1,1) >= k)
        {
            sf = mij-1;
            res = mij;
        }
        else
            in = mij+1;
    }

    return res;

}

#undef int
int main()
{
    int a,b,c;
    cin>>n>>k;

    for(int i=1;i<=n-1;i++)
    {
        cin>>a>>b>>c;

        G[a].push_back({b,c});
        G[b].push_back({a,c});
    }

    cout<<Search()<<'\n';

    return 0;
}

/*

5 7
1 2 1
1 3 1
3 4 10
3 5 2

*/