/* "بِسْمِ اللهِ الرَّحْمٰنِ الرَّحِيْمِ  " -In the name of Allah."
-------------------- A R I F ----------------------- */

#include<bits/stdc++.h>
// for order set ---------------------
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
#define        ordered_set   tree<ll, null_type, less<ll>, rb_tree_tag, tree_order_statistics_node_update>
#define        index_of(x) find_by_order(x) // index_of the value x
#define        number_of(x) order_of_key(x) // how many value are stricly less then x
// ------------------------------------
#define        int long long int 
#define        INF 1e18
#define        PI 3.141592653
#define        PB push_back 
#define        F first
#define        S second
#define        MP(x, y) push_back(make_pair(x, y))
#define        srt(v) sort(v.begin(), v.end())
#define        all(x) x.begin(), x.end()
#define        rsrt(v) reverse(v.begin(), v.end())
#define        no cout << "NO" << endl
#define        yes cout << "YES" << "\n"
#define        e "\n" 
#define        pair  vector< pair <int ,int> >
#define        deb(args...){string _s = #args;replace(_s.begin(), _s.end(), ',', ' ');stringstream _ss(_s);istream_iterator<string> _it(_ss);err(_it, args);}

using namespace std;

template <typename T>
ostream &operator;<<(ostream &os;, const vector<T> &v){ os << '{'; for (const auto &x : v) os << " " << x; return os << '}';}
void err(istream_iterator<string> it) {} template <typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args){ cerr << *it <<"  = " << a << endl; err(++it, args...);}
/*----------------------------------------------------------------------------------------*/
int expo(int a, int b, int mod) {int res = 1; while (b > 0) {if (b & 1)res = (res * a) % mod; a = (a * a) % mod; b = b >> 1;} return res;}
int mod_add(int a, int b, int m) {a = a % m; b = b % m; return (((a + b) % m) + m) % m;}
int mod_mul(int a, int b, int m) {a = a % m; b = b % m; return (((a * b) % m) + m) % m;}
int mod_sub(int a, int b, int m) {a = a % m; b = b % m; return (((a - b) % m) + m) % m;}
int mminvprime(int a, int b) {return expo(a, b - 2, b);}
int mod_div(int a, int b, int m) {a = a % m; b = b % m; return (mod_mul(a, mminvprime(b, m), m) + m) % m;}  //only for prime m
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int getRandomNumber(int l, int r) {return uniform_int_distribution<int>(l, r)(rng);}
bool isBitSet(int num, int bitPosition) { return (num & (1 << bitPosition)) > 0 ; }
/*----------------------------------------------------------------------------------------*/
//---------DFS----------------------------------------------------------------
const int mx = 1e6+7 ;
vector<int> g[mx] ;
int vis[mx] = {0} ;
int arr[mx] = {0} ;
void graph(int u , int v )
{
    g[u].PB(v) ; g[v].PB(u) ;
}
int k , final = 0 ;
void dfs(int node , int par)
{
    vis[node] = 1 ;
    if(g[node].size() == 1){
        arr[node] = 1 ;
    }
    for(auto it : g[node])
        if(!vis[it])
            dfs(it , node) ;
   std::map<int, int> mp;
   if(g[node].size() != 1){
        for(auto it : g[node]){
            mp[arr[it]]++;
        }
        if(par != -1  and g[par].size() == 1) mp[1]++;
        for(int i =1 ; i<= k ; i++){
            if(!mp[i]){
                arr[node] = i ;
                break ;
            }
        }
   }
}

void dfs2(int node , int value)
{
    vis[node] = 1 ;
    if(value == 1){
        arr[node] = 2 ;
    }else arr[node] = 1 ;
    for(auto it : g[node])
        if(!vis[it])
            dfs2(it , arr[node]) ;
}
void dfs3(int node , int value)
{
    vis[node] = 1 ;
    if(value == 1){
        arr[node] = 2 ;
    }else if(value == 1 and g[node].size() != 1){
        arr[node] = 3 ;
    }
    else arr[node] = 1 ;
    for(auto it : g[node])
        if(!vis[it])
            dfs3(it , arr[node]) ;
}
void Clear(int n)
{
  for(int i =0 ; i<=n ; i++)
  {
    vis[i] =0 ;
    arr[i] = 0 ;
    final = 0 ;
  }
}
int ok(int n )
{
    std::map<int, int> mp;
    for(int i =1 ; i<=n ; i++){
        mp[arr[i]]++ ;
    }
    int ind = 1 ;
    std::vector<int> v;
    for(auto it : mp){
        v.PB(it.S) ;
    }
    srt(v) ; rsrt(v) ;
    int ans = 0 ;
    for(auto it : v){
        ans += (it*ind);
        ind++ ;
    }
    return ans ;
}
//---------DFS----------------------------------------------------------------
void   solve()
{
    int n = 0 , m = 0 , ans = 0 , cnt  = 0 ;
    cin >> n >> k ;
    for(int i =0 ; i<n-1 ; i++){
        int u , v ;
        cin >> u >> v ;
        graph(u , v) ;
    }
    if(n == 1){
        cout << 1 << e ; return ;
    }
    if(k == 1){
        cout << -1 << e ; return ;
    }
    if(k>2){
        for(int i =1 ; i<= n ; i++)
            if(!vis[i])
                dfs(i, -1) ;
        ans = ok(n) ;
        Clear(n) ;
         for(int i= 1; i<=n ; i++)
            if(!vis[i])
                dfs2(i , 0) ;
        ans = min(ans , ok(n)) ;
          Clear(n) ;
         for(int i= 1; i<=n ; i++)
            if(!vis[i])
                dfs3(i , 0) ;
        ans = min(ans , ok(n)) ;
    }
    else{
        for(int i= 1; i<=n ; i++)
            if(!vis[i])
                dfs2(i , 0) ;
        ans = ok(n) ;
    }
    
    cout << ans << e ;
}
int32_t main()
{ 

    ios_base::sync_with_stdio(false);cin.tie(NULL);
    // freopen("input.txt", "r", stdin);
    // freopen("output.txt", "w", stdout);
    int test_case =1; 
    // cin >> test_case ; 
    int c = 0 ;
    while( test_case --)
    {
      // c ++ ; cout << "Case " << c << ": " ;
       solve() ;   
    }
}
//vector<int>::iterator lower, upper;
//lower = lower_bound(v.begin(), v.end(), value) - v.begin() ;
//upper = upper_bound(v.begin(), v.end(), value) - v.begin() ; --&gt;
// scanf("%s%d",s,&x) != EOF