#include <bits/stdc++.h>
#define forr(_a,_b,_c) for(_a = (_b); _a <= (_c); ++_a)
#define ford(_a,_b,_c) for(_a = (_b) + 1; _a --> (_c);)
#define forf(_a,_b,_c) for(_a = (_b); _a < (_c); ++_a)
#define st first
#define nd second
#define ll long long
#define ull unsigned long long
#define pii pair <int,int>
#define pll pair <ll,ll>
#define piii pair <int,pii>
#define vi vector <int>
#define pb push_back
#define mp make_pair
#define all(x) begin(x),end(x)
#define file "test"
using namespace std;
const int N = 1e6 + 5;
const ll oo = 1e9;
const ll mod = 1e9 + 7;
vector <ll> s[N];
vector <pll> a[N];
ll ans, h[N], f[N];
ll k;
void dfs (int u, int p){
f[u] = 1;
for (pii e : a[u]){
int v = e.st;
if (v != p){
h[v] = e.nd;
dfs(v,u);
if (s[v].size() > s[u].size())
swap(s[v],s[u]), swap (f[u], f[v]);
for (int j = 0; j < s[v].size(); j++){
int d = s[v].size() - j;
if (k - d > 0 && k - d < s[u].size())
ans = min (ans, s[v][j] + s[u][s[u].size() - (k - d)] + f[u] + f[v]);
}
for (int j = 0; j < s[v].size(); j++)
s[u][s[u].size() - (s[v].size() - j)] = min (s[u][s[u].size() - (s[v].size() - j)], s[v][j] - f[u] + f[v]);
}
}
s[u].pb(-f[u]);
for (int i = 1; i < h[u]; i++){
s[u].pb(oo);
}
f[u]++;
if (k < s[u].size())
ans = min (ans, s[u][s[u].size() - k] + f[u]);
// cout << u << " " << s[u].size() << " " << ans << " " << h[u] << " " << f[u] << "\n";
// for (int w : s[u])
// cout << w + f[u] << " ";
// cout << "\n";
}
int n,i,u,v,w;
int best_path (int nn, int kk, int edge[][2], int ww[]){
ans = oo;
n = nn;
k = kk;
if (k == 1)
return 0;
forf (i,0,n - 1){
u = edge[i][0];
v = edge[i][v];
w = ww[i];
a[u].pb({v,w});
a[v].pb({u,w});
}
dfs(0,0);
ans--;
return ((ans <= (n - 1)) ? ans : -1);
}
