#include <bits/stdc++.h>
using namespace std;
vector<int> g[100005];
bool vis[100005];
int leg[100005];
void dfs(int u, int p) {
  if (g[u].size() > 2) return;
  vis[u] = 1;
  for (int i = 0; i < g[u].size(); i++) {
    int v = g[u][i];
    if (v == p) continue;
    dfs(v, u);
  }
}
int main() {
  int n, a, b;
  scanf("%d", &n);
  for (int i = 2; i <= n; i++) {
    scanf("%d%d", &a, &b);
    g[a].push_back(b);
    g[b].push_back(a);
  }
  for (int i = 1; i <= n; i++)
    if (g[i].size() == 1) dfs(i, 0);
  for (int i = 1; i <= n; i++) {
    if (vis[i]) continue;
    for (int j = 0; j < g[i].size(); j++) {
      int v = g[i][j];
      if (!vis[v]) continue;
      leg[i] = min(leg[i] + 1, 2);
    }
  }
  bool ok = 1;
  for (int i = 1; i <= n; i++) {
    int cnt = 0;
    for (int j = 0; j < g[i].size(); j++) {
      int v = g[i][j];
      if (vis[v]) continue;
      if (g[v].size() - leg[v] > 1) cnt++;
    }
    if (cnt > 2) ok = 0;
  }
  if (ok)
    printf("Yes\n");
  else
    printf("No\n");
}

### Prompt

Develop a solution in CPP to the problem described below:

Limak is a little bear who learns to draw. People usually start with houses, fences and flowers but why would bears do it? Limak lives in the forest and he decides to draw a tree.

Recall that tree is a connected graph consisting of n vertices and n - 1 edges.

Limak chose a tree with n vertices. He has infinite strip of paper with two parallel rows of dots. Little bear wants to assign vertices of a tree to some n distinct dots on a paper so that edges would intersect only at their endpoints — drawn tree must be planar. Below you can see one of correct drawings for the first sample test.

<image>

Is it possible for Limak to draw chosen tree?

Input

The first line contains single integer n (1 ≤ n ≤ 105).

Next n - 1 lines contain description of a tree. i-th of them contains two space-separated integers ai and bi (1 ≤ ai, bi ≤ n, ai ≠ bi) denoting an edge between vertices ai and bi. It's guaranteed that given description forms a tree.

Output

Print "Yes" (without the quotes) if Limak can draw chosen tree. Otherwise, print "No" (without the quotes).

Examples

Input

8
1 2
1 3
1 6
6 4
6 7
6 5
7 8


Output

Yes


Input

13
1 2
1 3
1 4
2 5
2 6
2 7
3 8
3 9
3 10
4 11
4 12
4 13


Output

No

### Response

```cpp
#include <bits/stdc++.h>
using namespace std;
vector<int> g[100005];
bool vis[100005];
int leg[100005];
void dfs(int u, int p) {
  if (g[u].size() > 2) return;
  vis[u] = 1;
  for (int i = 0; i < g[u].size(); i++) {
    int v = g[u][i];
    if (v == p) continue;
    dfs(v, u);
  }
}
int main() {
  int n, a, b;
  scanf("%d", &n);
  for (int i = 2; i <= n; i++) {
    scanf("%d%d", &a, &b);
    g[a].push_back(b);
    g[b].push_back(a);
  }
  for (int i = 1; i <= n; i++)
    if (g[i].size() == 1) dfs(i, 0);
  for (int i = 1; i <= n; i++) {
    if (vis[i]) continue;
    for (int j = 0; j < g[i].size(); j++) {
      int v = g[i][j];
      if (!vis[v]) continue;
      leg[i] = min(leg[i] + 1, 2);
    }
  }
  bool ok = 1;
  for (int i = 1; i <= n; i++) {
    int cnt = 0;
    for (int j = 0; j < g[i].size(); j++) {
      int v = g[i][j];
      if (vis[v]) continue;
      if (g[v].size() - leg[v] > 1) cnt++;
    }
    if (cnt > 2) ok = 0;
  }
  if (ok)
    printf("Yes\n");
  else
    printf("No\n");
}

```