#include<bits/stdc++.h>
using namespace std;
#define int long long
const int N=2e5+10,inf=1e9;
vector<int>G[N];
int dp[N],k,sum,n,m;
void dfs(int x,int f)
{
	int mx=-inf,mn=0;dp[x]=0;
	for(int y:G[x])if(y!=f)
	{
		dfs(y,x);
		mx=max(mx,dp[y]+1);
		mn=min(mn,dp[y]+1);
	}
	if(mx+mn<0)dp[x]=mn;
	else if(mx>=k)dp[x]=-k-1,sum++;
	else dp[x]=(mx==-inf?0:mx);
	if(x==1&&dp[x]>=0)sum++;
}
bool check(int kk)
{
	k=kk,sum=0;
	dfs(1,0);
	return sum<=m;
}
signed main()
{
	cin>>n>>m;
	for(int i=1;i<n;i++)
	{
		int x,y;cin>>x>>y;
		G[x].push_back(y);
		G[y].push_back(x);
	}
	int l=1,r=n,ans=n;
	while(l<=r)
	{
		int mid=(l+r)>>1;
		if(check(mid))r=mid-1,ans=mid;
		else l=mid+1;
	}
	cout<<ans;
	return 0;
}