Heidi has finally found the mythical Tree of Life – a legendary combinatorial structure which is said to contain a prophecy crucially needed to defeat the undead armies.

On the surface, the Tree of Life is just a regular undirected tree well-known from computer science. This means that it is a collection of n points (called vertices), some of which are connected using n - 1 line segments (edges) so that each pair of vertices is connected by a path (a sequence of one or more edges).

To decipher the prophecy, Heidi needs to perform a number of steps. The first is counting the number of lifelines in the tree – these are paths of length 2, i.e., consisting of two edges. Help her!

Input

The first line of the input contains a single integer n – the number of vertices in the tree (1 ≤ n ≤ 10000). The vertices are labeled with the numbers from 1 to n. Then n - 1 lines follow, each describing one edge using two space-separated numbers a b – the labels of the vertices connected by the edge (1 ≤ a < b ≤ n). It is guaranteed that the input represents a tree.

Output

Print one integer – the number of lifelines in the tree.

Examples

Input

4
1 2
1 3
1 4


Output

3

Input

5
1 2
2 3
3 4
3 5


Output

4

Note

In the second sample, there are four lifelines: paths between vertices 1 and 3, 2 and 4, 2 and 5, and 4 and 5.
import java.util.*;

public class Main{
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);

        int n=in.nextInt();
        Vector<Integer> graph[];
        graph = new Vector[110000];
        for(int i=0;i<110000;++i){
            graph[i]=new Vector<>();
        }
        boolean []visit=new boolean[110000];
        Arrays.fill(visit, false);

        for(int i=0;i<n-1;++i){
            int x=in.nextInt(), y=in.nextInt();
            graph[x].add(y);
            graph[y].add(x);
        }

        int ans = 0;
        for(int i=1;i<=n;++i){
            int deg = graph[i].size();
            ans += ((deg*(deg-1))/2);
        }

        System.out.println(ans);
    }
}