#include <bits/stdc++.h>
using namespace std;
const double PI = acos(-1);
const long long mod = 1e9 + 7;
const long long N = 1e5 + 5, K = 105;
const int si = (1 << 20);
const long long add = 1e4;
const long long M = 100 + 5;
const double INFdb = 1e10;
int n;
vector<int> v[N];
bool check[N];
int legs[N];
void dfs(int u, int par) {
  if (v[u].size() <= 2) {
    check[u] = 1;
    for (int x : v[u]) {
      if (x != par) {
        dfs(x, u);
      }
    }
  }
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(0);
  cin >> n;
  for (int i = 1; i <= n - 1; ++i) {
    int x, y;
    cin >> x >> y;
    v[x].push_back(y);
    v[y].push_back(x);
  }
  for (int i = 1; i <= n; ++i) {
    if ((int)v[i].size() == 1) dfs(i, 0);
  }
  for (int i = 1; i <= n; ++i) {
    for (int x : v[i]) {
      if (check[x]) {
        legs[i] = min(legs[i] + 1, 2);
      }
    }
  }
  for (int i = 1; i <= n; ++i) {
    if (!check[i]) {
      int cnt = 0;
      for (int x : v[i]) {
        if (!check[x] && v[x].size() - legs[x] > 1) {
          ++cnt;
        }
      }
      if (cnt > 2) {
        return cout << "NO", 0;
      }
    }
  }
  cout << "YES";
  cerr << "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";
  return 0;
}
