write a go solution for Description:
You are given an undirected tree consisting of n vertices. An undirected tree is a connected undirected graph with n-1 edges.

Your task is to add the minimum number of edges in such a way that the length of the shortest path from the vertex 1 to any other vertex is at most 2. Note that you are not allowed to add loops and multiple edges.

Input Format:
The first line contains one integer n (2<=n<=2*10^5) — the number of vertices in the tree.

The following n-1 lines contain edges: edge i is given as a pair of vertices u_i,v_i (1<=u_i,v_i<=n). It is guaranteed that the given edges form a tree. It is guaranteed that there are no loops and multiple edges in the given edges.

Output Format:
Print a single integer — the minimum number of edges you have to add in order to make the shortest distance from the vertex 1 to any other vertex at most 2. Note that you are not allowed to add loops and multiple edges.

Note:
The tree corresponding to the first example:  The answer is 2, some of the possible answers are the following: [(1,5),(1,6)], [(1,4),(1,7)], [(1,6),(1,7)].

The tree corresponding to the second example:  The answer is 0.

The tree corresponding to the third example:  The answer is 1, only one possible way to reach it is to add the edge (1,3).. Output only the code with no comments, explanation, or additional text.