#include<bits/stdc++.h>

using namespace std;

#define setIO(s) freopen(s".in","r",stdin)

#define maxn 1000000

int n,S,edges,mid,cnt;

int hd[maxn],to[maxn<<1],nex[maxn<<1],dis[maxn];

void add(int u,int v)

{

    nex[++edges]=hd[u],hd[u]=edges,to[edges]=v;

}

void dfs(int u,int ff)

{

    if(cnt>S) return;

    int now=0;

    for(int i=hd[u];i;i=nex[i])

    {

        int v=to[i];

        if(v==ff) continue;

        dfs(v,u);

        if(now+dis[v] > mid)

        {

            ++cnt;

            now=min(now, dis[v]);

        }

        else now=max(now, dis[v]);

    }

    dis[u]=now+1;

}

int check()

{

    cnt=0;

    dfs(1,0);

    return cnt<=S;

}

int main()

{

    // setIO("input");

    int i,j;

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

    for(i=1;i<n;++i)

    {

        int a,b;

        scanf("%d%d",&a,&b);

        add(a,b),add(b,a);

    }

    int l=1,r=n,ans=0;

    while(l<=r)

    {

        mid=(l+r)>>1;

        if(check()) ans=mid, r=mid-1;

        else l=mid+1;

    }

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

    return 0;

}