#include<bits/stdc++.h>
using namespace std;
const int N=1e5+5;
int f[N],head[N],d[N],max_d[N],cnt=-1,ans[N];
int num,deep;
struct Edge
{
	int to,next;
}e[N];
inline void add(int u,int v)
{
	e[++cnt].to=v;
	e[cnt].next=head[u];
	head[u]=cnt;
}
void dfs(int u,int fa)
{
	d[u]=d[fa]+1;
	max_d[u]=d[u];
	f[u]=fa;
	if(deep<d[u])
	{
		deep=d[u];
		num=u;
	}
	for(int i=head[u];i!=-1;i=e[i].next)
	{
		int v=e[i].to;
		if(v==fa) continue;
		dfs(v,u);
		max_d[u]=max(max_d[u],max_d[v]);
	}
}
inline int read()
{
	int f=1,x=0; char s;
	do{s=getchar();if(s=='-')f=-1;}while(s<'0'||s>'9');
	do{x=(x<<1)+(x<<3)+s-48;s=getchar();}while(s>='0'&&s<='9');
	return f*x;
}
inline void write(int num)
{
	if(num<0) putchar('-'),num=-num;
	if(num>10) write(num/10);
	putchar(num%10+48);
}
bool cmp(int a,int b)
{
	return a>b;
}
int main()
{
	memset(head,-1,sizeof(head));
	int n,k; n=read(); k=read();
	for(int i=1;i<=n-1;i++)
	{
		int u,v;
		u=read(); v=read();
		add(u,v); add(v,u);
	}
	deep=-1;
	dfs(1,0);
	deep=-1;
	dfs(num,0);
	for(int i=1;i<=(d[num]+1)/2;i++)
		num=f[num];
	memset(max_d,0,sizeof(max_d));
	dfs(num,0);
	for(int i=1;i<=n;i++)
		ans[i]=max_d[i]-d[i]+1;
	sort(ans+1,ans+n+1,cmp);
	int ans_f;
	for(int i=k+1;i<=n;i++)
		ans_f=max(ans_f,ans[i]);
	cout<<ans_f;
}

题目样例过了 自编样例也过了 就是过不了测试