#include<bits/stdc++.h>

using namespace std;

const int MAXN = 2e5 + ;

const int MAXM = 2e5 + ;

int to[MAXM << ], nxt[MAXM << ], Head[MAXN], ed = ;

int cost[MAXM << ];

int ok[];

inline void addedge(int u, int v, int c) {

        to[++ed] = v;

        cost[ed] = c;

        nxt[ed] = Head[u];

        Head[u] = ed;

}

inline void ADD(int u, int v, int c) {

        addedge(u, v, c);

        addedge(v, u, c);

}

int n, anser, k, cnt;

int sz[MAXN], f[MAXN], dep[MAXN], sumsz, root;

bool vis[MAXN];

pair<int, int> o[MAXN];

int num[MAXN];

void getroot(int x, int fa) {

        sz[x] = ;

        f[x] = ;

        for (int i = Head[x]; i; i = nxt[i]) {

                int v = to[i];

                if (v == fa || vis[v]) {

                        continue;

                }

                getroot(v, x);

                sz[x] += sz[v];

                f[x] = max(f[x], sz[v]);

        }

        f[x] = max(f[x], sumsz - sz[x]);

        if (f[x] < f[root]) {

                root = x;

        }

}

void getdeep(int x, int fa, int deep) {

        if (dep[x] > k) {

                return;

        }

        o[++cnt] = make_pair(dep[x], deep);

        num[++num[]] = dep[x];

        for (int i = Head[x]; i; i = nxt[i]) {

                int v = to[i];

                if (v == fa || vis[v]) {

                        continue;

                }

                dep[v] = dep[x] + cost[i];

                getdeep(v, x, deep + );

        }

}

void calc(int x, int d) {

        num[] = ;

        dep[x] = d;

        for (int i = Head[x]; i; i = nxt[i]) {

                int v = to[i];

                if (vis[v]) {

                        continue;

                }

                cnt = ;

                dep[v] = dep[x] + cost[i];

                getdeep(v, x, );

                for (int j = ; j <= cnt; j++) {

                        if (o[j].first <= k) {

                                if (ok[k - o[j].first] != INT_MAX) {

                                        anser = min(anser, ok[k - o[j].first] + o[j].second);

                                }

                        }

                }

                for (int j = ; j <= cnt; j++) {

                        if (o[j].first <= k) {

                                ok[o[j].first] = min(o[j].second, ok[o[j].first]);

                        }

                }

        }

        for (int i = ; i <= num[]; i++) {

                ok[num[i]] = INT_MAX;

        }

}

void solve(int x) {

        vis[x] = ;

        calc(x, );

        int totsz = sumsz;

        for (int i = Head[x]; i; i = nxt[i]) {

                int v = to[i];

                if (vis[v]) {

                        continue;

                }

                root = ;

                sumsz = sz[v] > sz[x] ? totsz - sz[x] : sz[v];

                getroot(v, );

                solve(root);

        }

}

int main() {

        scanf("%d %d", &n, &k);

        anser = INT_MAX;

        for (int i = ; i <= k; i++) {

                ok[i] = INT_MAX;

        }

        cnt = ;

        memset(Head, , sizeof(Head));

        memset(vis, , sizeof(vis));

        ed = ;

        int u, v, c;

        for (int i = ; i < n; i++) {

                scanf("%d %d %d", &u, &v, &c);

                ADD(u + , v + , c);

        }

        root = , sumsz = f[] = n;

        getroot(, );

        solve(root);

        printf("%d\n", anser == INT_MAX ? - : anser);

        return ;

}