#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n;
  cin >> n;
  vector<vector<int> > adj(n, vector<int>(n, 0));
  set<int> s;
  int x;
  for (int i = 2; i < n + 1; i++) {
    cin >> x;
    adj[x - 1][i - 1] = 1;
    s.insert(x - 1);
  }
  stack<int> st;
  int i = 0;
  int j;
  int count = 0;
  while (i < n) {
    if (s.find(i) == s.end()) {
      i++;
      continue;
    }
    for (j = 0; j < n; j++) {
      if (adj[i][j] == 1 && (s.find(j) == s.end())) {
        count++;
      }
    }
    if (count < 3) {
      cout << "No" << endl;
      return 0;
    }
    count = 0;
    i++;
  }
  cout << "Yes" << endl;
  return 0;
}
