#include <bits/stdc++.h>
using namespace std;
const int N = 112345;
vector<int> v[N];
int read() {
  int x;
  scanf("%d", &x);
  return x;
}
int cnt[N];
bool used[N];
bool t[N];
bool never[N];
int main() {
  int n, m, i, j, x, y;
  n = read();
  for (i = 2; i <= n; i++) {
    x = read();
    y = read();
    v[x].push_back(y);
    cnt[x]++;
    cnt[y]++;
    v[y].push_back(x);
  }
  queue<int> q;
  for (int i = 1; i <= n; i++) {
    if (cnt[i] == 1) {
      q.push(i);
      used[i] = 1;
    }
  }
  while (!q.empty()) {
    int x = q.front();
    q.pop();
    for (int i = 0; i < v[x].size(); i++) {
      int to = v[x][i];
      if (!used[to]) {
        if (cnt[to] <= 2 && !t[x] && !never[to]) {
          used[to] = 1;
          q.push(to);
        } else if (cnt[to] == 3 && !t[x] && !never[to]) {
          t[to] = 1;
        } else {
          never[to] = 1;
        }
        cnt[to]--;
      }
    }
  }
  for (i = 1; i <= n; i++) {
    if (cnt[i] >= 3) {
      puts("no");
      return 0;
    }
  }
  puts("yes");
}
