#include<bits/stdc++.h>
using namespace std;
const int N=1e5+5;
int n,k,mxlong,root,mid,deep[N],godeep[N],l[N],ans;
vector<int> tr[N],zhijing,zj;

bool cmp(int x,int y)
{
	return x>y;
}

void dfs_zhijing(int now,int father,int juli)
{
	zhijing.push_back(now);
	if(juli>mxlong)
		mxlong=juli,root=now,zj=zhijing;
	for(auto v:tr[now])
	{
		if(v==father)
			continue;
		dfs_zhijing(v,now,juli+1);
	}
	zhijing.pop_back();
}

void dfs_deep(int now,int dp,int father)
{
	deep[now]=dp;
	godeep[now]=dp;
	for(auto v:tr[now])
	{
		if(v==father)
			continue;
		dfs_deep(v,dp+1,now);
		godeep[now]=max(godeep[now],godeep[v]);
	}
}

int main()
{
	cin>>n>>k;
	for(int i=2;i<=n;i++)
	{
		int u,v;
		cin>>u>>v;
		tr[u].push_back(v);
		tr[v].push_back(u);
	}
	
	dfs_zhijing(1,-1,0);
	mxlong=0;
	dfs_zhijing(root,-1,0);
	//	for(auto v:zj)
	//		cout<<v<<' ';
	mid=zj[zj.size()/2];
	
	dfs_deep(1,0,-1);
	
	for(int i=1;i<=n;i++)
		l[i]=godeep[i]-deep[i];
	sort(l+1,l+n+1,cmp);
	for(int i=k+1;i<=n;i++)
		ans=max(ans,l[i]+1);
	cout<<ans;
}