#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
#define REP(i,n) for(int i=0,_n=(int)(n);i<_n;++i)
#define ALL(v) (v).begin(),(v).end()
#define CLR(t,v) memset(t,(v),sizeof(t))
template<class T1,class T2>ostream& operator<<(ostream& os,const pair<T1,T2>&a){return os<<"("<<a.first<<","<<a.second<< ")";}
template<class T>void pv(T a,T b){for(T i=a;i!=b;++i)cout<<(*i)<<" ";cout<<endl;}
template<class T>void chmin(T&a,const T&b){if(a>b)a=b;}
template<class T>void chmax(T&a,const T&b){if(a<b)a=b;}


int nextInt() { int x; scanf("%d", &x); return x;}
ll nextLong() { ll x; scanf("%lld", &x); return x;}

const int MAX_N = 112345;
vector<int> g[MAX_N];
int dist[MAX_N];
int C[MAX_N];

void dfs(int cur, int prev, int d) {
  dist[cur] = d;
  for (int nxt : g[cur]) if (nxt != prev) {
    dfs(nxt, cur, d+1);
  }
}
int main2() {
  REP(i, MAX_N) g[i].clear();
  CLR(C, 0);


  int N = nextInt();
  int K = nextInt();
  REP(i, N-1) {
    int a = nextInt() - 1;
    int b = nextInt() - 1;
    g[a].push_back(b);
    g[b].push_back(a);
  }
  if (N < K) {
    cout << -1 << endl;
    return 0;
  }

  dfs(0, -1, 0);

  REP(i, N) C[ dist[i] ]++;
  ll ans = 0;
  REP(i, N) {
    int x = min(K, C[i]);
    K -= x;
    ans += x;
  }
  cout << ans-1 << endl;
  return 0;
}

int main() {

#ifdef LOCAL
  for (;!cin.eof();cin>>ws)
#endif
    main2();
  return 0;
}