#include <iostream>
#include <vector>
using namespace std;
struct Side { int idx, val; };
struct node { vector<Side> side; };
vector<node> view;
vector<vector<int>> f_dis;
vector<Side> dia;
int n, s, top, max_dis = -1, ans = 99999999;
void read()
{
    cin >> n >> s;
    view.resize(n);
    f_dis = vector<vector<int>>(n, vector<int>(n, -1));
    int a, b, val;
    for(int i = 1; i < n; i++)
        cin >> a >> b >> val, view[--a].side.push_back({--b, val}), view[b].side.push_back({a, val});
}
int farthest_dis(const int &idx, const int &last)
{
    if(f_dis[idx][last] != -1)
        return f_dis[idx][last];
    int get = 0;
    for(int i = 0; i < view[idx].side.size(); i++)
        if(view[idx].side[i].idx != last)
            get = max(get, view[idx].side[i].val + farthest_dis(view[idx].side[i].idx, idx));
    f_dis[idx][last] = get;
    return get;
}
void find_top(int idx)
{
    int last = -1;
    while(view[idx].side.size() > 1)
    {
        int get = -1, next = -1;
        for(int i = 0; i < view[idx].side.size(); i++)
            if(view[idx].side[i].idx != last && farthest_dis(view[idx].side[i].idx, idx) > get)
                get = farthest_dis(view[idx].side[i].idx, idx), next = view[idx].side[i].idx;
        last = idx;
        idx = next;
    }
    top = idx;
}
void set_dia(int idx)
{
    int last = -1;
    while(true)
    {
        int get = -1, next = -1, val = -1;
        for(int i = 0; i < view[idx].side.size(); i++)
            if(view[idx].side[i].idx != last && view[idx].side[i].val + farthest_dis(view[idx].side[i].idx, idx) > get)
                get = view[idx].side[i].val + farthest_dis(view[idx].side[i].idx, idx), next = view[idx].side[i].idx, val = view[idx].side[i].val;
        dia.push_back({idx, val});
        if(view[idx].side.size() == 1 && view[idx].side[0].idx == last)
            break;
        last = idx;
        idx = next;
    };
}
int main()
{
    read();
    find_top(0);
    set_dia(top);
    vector<vector<int>> sum(n, vector<int>(n, 0));
    for(int i = 0; i < dia.size(); i++)
        for(int j = i + 1; j < dia.size(); j++)
            sum[i][j] = sum[i][j - 1] + dia[j - 1].val;
    for(int i = 0; i < dia.size(); i++)
    {
        for(int j = i; j < dia.size(); j++)
        {
            if(sum[i][j] > s)
                continue;
            int get = 0;
            for(int k = i; k <= j; k++)
            {
                for(int l = 0; l < view[dia[k].idx].side.size(); l++)
                {
                    //cout << dia[i].idx << "(i=" << i << ")-" << dia[j].idx << "(j=" << j << ") =" << view[dia[k].idx].side[l].val + farthest_dis(view[dia[k].idx].side[l].idx, dia[k].idx) << '\n';
                    if(view[dia[k].idx].side[l].idx != (k == i ? -1 : dia[k - 1].idx) && view[dia[k].idx].side[l].idx != (k == j ? -1 : dia[k + 1].idx))
                        get = max(get, view[dia[k].idx].side[l].val + farthest_dis(view[dia[k].idx].side[l].idx, dia[k].idx));
                }
            }
            ans = min(ans, get);
        }
    }
    cout << ans << '\n';
    // for(int i = 0; i < dia.size(); i++)
    //     for(int j = i; j < dia.size(); j++)
    //     {
    //         cout << i << '-' << j << ": " << sum[i][j] << '\n';
    //     }
    return 0;
}