#include <cstdio>

#include <algorithm>

#include <cstring>

#include <queue>

#include <deque>

const int N = 300 + 9;

struct edge{int next,link,w;}es[N*2];

std::deque<int>q;

int dis[N],d_len,len[N],pre[N],p[N],f[N],max_dis[N],ec,son[N],n,s,ans = 0x7fffffff;

bool mark[N];

inline void addedge(const int x,const int y,const int z)

{

	es[++ec].next = son[x];

	son[x] = ec;

	es[ec].link = y;

	es[ec].w = z;

}

inline void Addedge(const int x,const int y,const int z){addedge(x,y,z);addedge(y,x,z);}

int bfs(const int s)

{

	memset(dis,0,sizeof dis);

	memset(pre,0,sizeof pre);

	static std::queue<int>q;

	for (q.push(s); !q.empty(); ) {

		const int u = q.front(); q.pop();

		for (int i = son[u]; i; i = es[i].next) {

			const int v = es[i].link;

			if (v == s || dis[v]) continue;

			dis[v] = dis[u] + es[i].w;

			pre[v] = u;

			q.push(v);

		}

	}

	int res = 1;

	for (int i = 1; i <= n; ++i) if (dis[i] > dis[res]) res = i;

	return res;

}

void find_diameter()

{

	int t,s;

	d_len = dis[t = bfs(s = bfs(1))];

	while (t) {

		mark[t] = true;

		p[++p[0]] = t;

		len[p[0]] = dis[t] - dis[pre[t]];

		t = pre[t];

	}

}

void dp(const int u,const int fa)

{

	for (int i = son[u]; i; i = es[i].next) {

		if (mark[es[i].link] || es[i].link == fa) continue;

		dp(es[i].link,u);

		f[u] = std::max(f[es[i].link] + es[i].w,f[u]);

	}

}

int calc_dis(const int u)

{

	memset(f,0,sizeof f);

	dp(u,0);

	return f[u];

}

int main()

{

	#ifndef ONLINE_JUDGE

	freopen("core.in","r",stdin);

	freopen("core.out","w",stdout);

	#endif

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

	for (int i = 1,x,y,z; i < n; ++i) {

		scanf("%d%d%d",&x,&y,&z);

		Addedge(x,y,z);

	}

	find_diameter();

	for (int i = 1; i <= p[0]; ++i) {

		max_dis[i] = calc_dis(p[i]);

		//printf("%d\n",max_dis[i]);

	}

	for (int i = 1,head = 1,sum = 0,front_dis = 0,tail_dis = 0; i <= p[0]; ++i) {

		sum += len[i - 1];

		tail_dis += len[i - 1];

		while (sum > s) {

			front_dis += len[head];

			sum -= len[head++];

		}

		while (q.size() && q.front() < head) q.pop_front();

		while (q.size() && max_dis[q.back()] <= max_dis[i]) q.pop_back();

		q.push_back(i);

		if (q.size()) ans = std::min(ans,std::max(max_dis[q.front()],std::max(d_len - tail_dis,front_dis)));

	}

	printf("%d\n",ans);

}