#include <iostream>
using namespace std;

const int maxn = 310, INF = 0x3f3f3f3f;
int dis[maxn][maxn];

int main() {
    int n, s;
    cin >> n >> s;
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= n; j++) {
            if (i != j)
                dis[i][j] = INF;
            else
                dis[i][j] = 0;
        }
    for (int i = 1; i < n; i++) {
        int from, to, length;
        cin >> from >> to >> length;
        dis[from][to] = dis[to][from] = length;
    }
    for (int k = 1; k <= n; k++)
        for (int i = 1; i <= n; i++)
            for (int j = 1; j <= n; j++)
                if (i != j && j != k && i != k)
                    dis[i][j] = min(dis[i][j], dis[i][k] + dis[k][j]);
    int maxlen = 0;
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= n; j++)
            maxlen = max(maxlen, dis[i][j]);
    int res = INF;
    for (int i = 1; i <= n; i++)
        for (int j = i; j <= n; j++)
            if (dis[i][j] == maxlen) {
                for (int k = 1; k <= n; k++)
                    if (dis[i][k] + dis[k][j] == dis[i][j])
                        for (int x = 1; x <= n; x++)
                            if (dis[i][x] + dis[x][j] == dis[i][j] && dis[k][x] <= s)
                                res = min(res, max(min(dis[k][i], dis[x][i]), min(dis[j][k], dis[j][x])));
            }
    cout << res << endl;
    return 0;
}