B'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. The first line contains one integer n -- the number of vertices in the tree (3 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89n xe2 x80 x89 xe2 x89 xa4 xe2 x80 x891 xe2 x80 x89000). Each of the next n xe2 x80 x89- xe2 x80 x891 lines contains one integer pi (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89i xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89n xe2 x80 x89- xe2 x80 x891) -- the index of the parent of the i xe2 x80 x89+ xe2 x80 x891-th vertex (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89pi xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89i). Vertex 1 is the root. It 's guaranteed that the root has at least 2 children. 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: '...