/** Solutie buna - Gabriel Robert Inelus*/
#include <bits/stdc++.h>

#define Nmax 100005
#define Maxcost (1<<29)

using namespace std;
vector<pair<int,int> > G[Nmax];
int Daddy[Nmax][18],Cost[Nmax][18],level[Nmax];
int Root,N;
long long X;
bitset<Nmax> used;

void Read()
{
    scanf("%d%lld",&N,&X);
    Root = 1;
    level[Root] = 1;
    Daddy[Root][0] = 0;
    Cost[Root][0] = 1<<30;
    int a,b,c;
    for(int i = 1; i < N; ++i)
    {
        scanf("%d%d%d",&a,&b,&c);
        G[a].push_back({b,c});
        G[b].push_back({a,c});
    }
}

void DFS(int k)
{
    used[k] = 1;
    for(auto it : G[k])
        if(!used[it.first]){
            level[it.first] = level[k] + 1;
            Daddy[it.first][0] = k;
            Cost[it.first][0] = it.second;
            DFS(it.first);
        }
}

void BuildRootDp()
{
    for(int step = 1; step <= 17; ++step)
        for(int node = 1; node <= N; ++node)
        {
            Daddy[node][step] = Daddy[Daddy[node][step - 1]][step - 1];
            Cost[node][step] = Cost[node][step - 1] + Cost[Daddy[node][step - 1]][step-1];
        }
}

int Query(int node, long long value)
{
    int step = 0,saved = node;
    while(Cost[node][step + 1] <= value)
        ++step;
    while(step >= 0 && value >= Cost[node][step])
    {
        value -= Cost[node][step];
        node = Daddy[node][step];
        while(step >= 0 && Cost[node][step] > value)
            --step;
    }
    return level[saved] - level[node];
}

long long Count(long long value)
{
    long long rez = 0;
    for(int i = 1; i <= N; ++i)
        rez += Query(i,value);
    return rez;
}

long long Solve(long long kth)
{
    long long li,lf,m,value;
    li = 0;
    lf = Maxcost;
    while(li <= lf)
    {
        m = li + ((lf - li) >> 1);
        value = Count(m);
        if(value < kth)
            li = m + 1;
        else
            lf = m - 1;
    }
    return li;
}

int main()
{
    ///freopen("treert.in","r",stdin);
    ///freopen("treert.out","w",stdout);
    Read();
    DFS(Root);
    BuildRootDp();
    long long res = Solve(X);
    if(res >= (1 << 29))
        printf("-1\n");
    else
        printf("%lld\n",res);

    return 0;
}