Someone give a strange birthday present to Ivan. It is hedgehog — connected undirected graph in which one vertex has degree at least 3 (we will call it center) and all other vertices has degree 1. Ivan thought that hedgehog is too boring and decided to make himself k-multihedgehog.

Let us define k-multihedgehog as follows:

  * 1-multihedgehog is hedgehog: it has one vertex of degree at least 3 and some vertices of degree 1.
  * For all k ≥ 2, k-multihedgehog is (k-1)-multihedgehog in which the following changes has been made for each vertex v with degree 1: let u be its only neighbor; remove vertex v, create a new hedgehog with center at vertex w and connect vertices u and w with an edge. New hedgehogs can differ from each other and the initial gift. 



Thereby k-multihedgehog is a tree. Ivan made k-multihedgehog but he is not sure that he did not make any mistakes. That is why he asked you to check if his tree is indeed k-multihedgehog.

Input

First line of input contains 2 integers n, k (1 ≤ n ≤ 10^{5}, 1 ≤ k ≤ 10^{9}) — number of vertices and hedgehog parameter.

Next n-1 lines contains two integers u v (1 ≤ u,    v ≤ n;    u ≠ v) — indices of vertices connected by edge.

It is guaranteed that given graph is a tree.

Output

Print "Yes" (without quotes), if given graph is k-multihedgehog, and "No" (without quotes) otherwise.

Examples

Input

14 2
1 4
2 4
3 4
4 13
10 5
11 5
12 5
14 5
5 13
6 7
8 6
13 6
9 6


Output

Yes


Input

3 1
1 3
2 3


Output

No

Note

2-multihedgehog from the first example looks like this:

<image>

Its center is vertex 13. Hedgehogs created on last step are: [4 (center), 1, 2, 3], [6 (center), 7, 8, 9], [5 (center), 10, 11, 12, 13].

Tree from second example is not a hedgehog because degree of center should be at least 3.
#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e5 + 10;
int n, m;
set<int> G[maxn];
int cnt[maxn];
void solve() {
  set<int> leave;
  leave.clear();
  for (int i = 1; i <= n; i++) {
    if (G[i].size() == 1) leave.insert(i);
  }
  bool flag = true;
  while (n > 1) {
    set<int> pre;
    for (auto& it : leave) {
      int p = *G[it].begin();
      G[p].erase(it), cnt[p]++, n--;
      pre.insert(p);
    }
    leave.clear();
    for (auto& it : pre) {
      if (cnt[it] < 3) {
        flag = false;
        break;
      }
      cnt[it] = 0;
    }
    swap(leave, pre), m--;
  }
  if (!flag)
    cout << "No" << endl;
  else {
    if (m != 0)
      cout << "No" << endl;
    else
      cout << "Yes" << endl;
  }
}
int main() {
  ios::sync_with_stdio(false);
  int u, v;
  cin >> n >> m;
  for (int i = 1; i <= n - 1; i++) {
    cin >> u >> v;
    G[u].insert(v), G[v].insert(u);
  }
  solve();
  return 0;
}
