CF913B Christmas Spruce

Consider a rooted tree. A rooted tree has one special vertex called the root. All edges are directed from the root. Vertex $ u $ is called a child of vertex $ v $ and vertex $ v $ is called a parent of vertex $ u $ if there exists a directed edge from $ v $ to $ u $ . A vertex is called a leaf if it doesn't have children and has a parent. Let's call a rooted tree a spruce if its every non-leaf vertex has at least $ 3 $ leaf children. You are given a rooted tree, check whether it's a spruce. The definition of a rooted tree can be found [here](https://goo.gl/1dqvzz).

The first line contains one integer $ n $ — the number of vertices in the tree ( $ 3

Print "Yes" if the tree is a spruce and "No" otherwise.

The first example:  The second example:  It is not a spruce, because the non-leaf vertex $ 1 $ has only $ 2 $ leaf children. The third example: