comet#8

#include<bits/stdc++.h>
using namespace std;
const int N=1e5+333;
vector<int>v[N];
int dep1[N],dep2[N];
int maxd1,maxd2;
int n;
struct re{
    int poi,val;
    bool operator    <(const re &az)const{
        return val<az.val;
    }
};
priority_queue<re>s;
int dfs1(int fath,int x){
    dep1[x]=dep1[fath]+1;
    if(dep1[x]>dep1[maxd1])maxd1=x;
    for(int i=0;i<v[x].size();i++){
        int dot=v[x][i];
        if(dot==fath)continue;
        dfs1(x,dot);
    }
}
int dfs2(int fath,int x){
    dep2[x]=dep2[fath]+1;
    if(dep2[x]>dep2[maxd2])maxd2=x;
        for(int i=0;i<v[x].size();i++){
        int dot=v[x][i];
        if(dot==fath)continue;
        dfs2(x,dot);
    }
}
int f[N];
int tr(int fath,int x){
    for(int i=0;i<v[x].size();i++){
        int dot=v[x][i];
        if(dot==fath)continue;
        tr(x,dot);
        f[x]=max(f[x],f[dot]+1);
    }
}
int dist,vot,k,cnt;
bool p[N];
int main(){
    //freopen("p.in","r",stdin);
    //freopen("p.out","w",stdout);
    cin>>n>>k;
    if(n==k){cout<<0;return 0;}
    for(int i=1;i<n;i++){
        int a,b;
        cin>>a>>b;
        v[a].push_back(b);
        v[b].push_back(a);
    }
    dfs1(0,1);
    dfs2(0,maxd1);
    dist=dep2[maxd2]-1;
    for(int i=1;i<=n;i++){
        int l=dep1[maxd1]-dep1[i];
        if(dist/2==l){vot=i;break;}
    }
    tr(0,vot);
    re zl;
    for(int i=0;i<v[vot].size();i++){
        int dot=v[vot][i];
        zl.poi=dot;zl.val=f[dot];
        s.push(zl);
        p[dot]=1;
    }
    cnt=0;p[vot]=1;
    
    while(cnt<k){
        cnt++;
        zl=s.top();
        s.pop();
        int x=zl.poi;
        p[x]=1;
        for(int i=0;i<v[x].size();i++){
            int dot=v[x][i];
            if(p[dot])continue;
            zl.poi=dot;zl.val=f[dot];
            s.push(zl);
            p[dot]=1;
        }
    }
    sort(f+1,f+1+n);
    cout<<f[n-k-1]+1;
    return 0;
}