#include <bits/stdc++.h>
using namespace std;
inline long long read() {
  long long x = 0;
  int ch = getchar(), f = 1;
  while (!isdigit(ch) && (ch != '-') && (ch != EOF)) ch = getchar();
  if (ch == '-') {
    f = -1;
    ch = getchar();
  }
  while (isdigit(ch)) {
    x = (x << 1) + (x << 3) + ch - '0';
    ch = getchar();
  }
  return x * f;
}
const int N = 1e5 + 10;
int n, x, y;
bool vis[N];
int tot, first[N], to[N << 1], last[N << 1];
inline void Add(int x, int y) {
  to[++tot] = y, last[tot] = first[x], first[x] = tot;
}
bool flag;
int dp[N];
inline void dfs(int u, int fa) {
  int cnt = 0;
  for (register int i = first[u]; i; i = last[i]) {
    int v = to[i];
    if (v != fa) dfs(v, u), dp[u] += dp[v], ++cnt;
  }
  if (dp[u] == 2 && cnt == 1 || !dp[u]) ++dp[u];
}
inline void Dfs(int u, int fa, int f) {
  int sum = 0;
  if (f > 2) ++sum;
  for (register int i = first[u]; i; i = last[i]) {
    int v = to[i];
    if (v != fa) {
      int tmp = max(1, f + dp[u] - dp[v]);
      if (tmp == 2 && f == 2) tmp = 3;
      Dfs(v, u, tmp);
      if (dp[v] > 2) sum++;
    }
  }
  if (sum > 2) flag = 0;
}
int main() {
  n = read();
  for (register int i = (1); i <= (n - 1); i++)
    x = read(), y = read(), Add(x, y), Add(y, x);
  flag = 1, dfs(1, 0), Dfs(1, 0, 0);
  puts(flag ? "YES" : "NO");
}
