#include<map>

#include<stack>

#include<queue>

#include<cstdio>

#include<string>

#include<vector>

#include<cstring>

#include<complex>

#include<iostream>

#include<assert.h>

#include<algorithm>

using namespace std;

#define inf 1001001001

#define infll 1001001001001001001LL

#define ll long long

#define dbg(vari) cerr<<#vari<<" = "<<(vari)<<endl

#define gmax(a,b) (a)=max((a),(b))

#define gmin(a,b) (a)=min((a),(b))

#define Ri register int

#define gc getchar()

#define il inline

il int read(){

    bool f=true;Ri x=0;char ch;while(!isdigit(ch=gc))if(ch=='-')f=false;while(isdigit(ch)){x=(x<<1)+(x<<3)+ch-'0';ch=gc;}return f?x:-x;

}

#define gi read()

#define FO(x) freopen(#x".in","r",stdin),freopen(#x".out","w",stdout);

struct edge{

    int to,next;

}e[233333];

int last[100005],ecnt,cnt,n,k,lb,rb,mid,ans;

int f[100005],_a,a[100005];

int dfs(int x,int fa=0){

    f[x]=0;

    //...

    for(int i=last[x];i;i=e[i].next)if(e[i].to!=fa)dfs(e[i].to,x);

    _a=a[0]=0;

    for(int i=last[x];i;i=e[i].next)if(e[i].to!=fa)a[++_a]=f[e[i].to]+1;

    sort(a+1,a+_a+1);

    while(_a&&a[_a]+a[_a-1]>mid)_a--,ans++;

    f[x]=a[_a];

}

bool chk(){

    ans=0;

    dfs(1);

    return ans<=k;

}

int main(){

    n=gi;k=gi;

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

        int a=gi,b=gi;

        e[++ecnt]=(edge){b,last[a]};last[a]=ecnt;

        e[++ecnt]=(edge){a,last[b]};last[b]=ecnt;

    }

    int ans=n,lb=1,rb=n;

    while(lb<=rb){

        mid=(lb+rb)/2;

        if(chk()){

            ans=mid;

            rb=mid-1;

        }else{

            lb=mid+1;

        }

    }

    printf("%d",ans);

    return 0;

}