#include <bits/stdc++.h>
using namespace std;
#define int long long
template<typename T>
void fin(T a){
  cout<<a<<endl;
  exit(0);
}
typedef pair<int,int> P;

signed main(){
  int n,k;cin>>n>>k;
  vector<int> edge[n];
  for(int i=0;i<n-1;i++){
    int u,v;cin>>u>>v;u--;v--;
    edge[u].push_back(v);
    edge[v].push_back(u);
  }
  if(n<k)fin(-1);
  int ans=0,cnt=0;
  queue<P> que;
  que.push(P(0,0));
  vector<int> used(n,0);
  while(cnt<k){
    P p=que.front();que.pop();
    ans+=p.second*(p.second+1)/2;
    cnt++;
    used[p.first]=1;
    for(int q:edge[p.first]){
      if(used[q])continue;
      que.push(P(q,p.second+1));
    }
  }
  cout<<ans<<endl;
}