#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 1;
int n, m, dist[N], root = -1;
vector<int> ve[N];
bool ok = 1, ok1 = 0;
stack<int> st;
void dfs(int u, int par) {
  if (ok1) return;
  if (st.size() == 2 * m - 1) {
    while (st.size() > m) st.pop();
    root = st.top();
    ok1 = 1;
    return;
  }
  int v;
  for (int i = 0; i < ve[u].size(); i++) {
    v = ve[u][i];
    if (v == par) continue;
    if (ve[v].size() >= 3) {
      st.push(v);
      dfs(v, u);
      if (!st.empty()) st.pop();
    }
  }
}
void dfs1(int u) {
  int v;
  for (int i = 0; i < ve[u].size(); i++) {
    v = ve[u][i];
    if (dist[v] != 0) continue;
    if (ve[v].size() == 1) {
      if (dist[u] != m) ok = 0;
    } else if (ve[v].size() == 2)
      ok = 0;
    else if (ve[v].size() == 3)
      ok = 0;
    else {
      dist[v] = dist[u] + 1;
      if (dist[v] > m)
        ok = 0;
      else
        dfs1(v);
    }
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cin >> n >> m;
  int u, v;
  for (int i = 1; i < n; i++) {
    cin >> u >> v;
    ve[u].push_back(v);
    ve[v].push_back(u);
  }
  u = -1;
  for (int i = 1; i <= n; i++) {
    if (ve[i].size() == 1) {
      u = ve[i][0];
      break;
    }
  }
  if (u == -1 || ve[u].size() < 3)
    ok = 0;
  else {
    st.push(u);
    dfs(u, 0);
    if (root == -1)
      ok = 0;
    else {
      dist[root] = 1;
      dfs1(root);
    }
  }
  if (!ok)
    cout << "NO" << '\n';
  else
    cout << "YES" << '\n';
}
