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.ArrayList;
import java.util.Scanner;

/**
 *
 * @author Rishabh
 */
public class Main {
    public static void main(String[] args) {
        Scanner s=new Scanner(System.in);
        int n=s.nextInt();
        ArrayList<Integer> gr[]=new ArrayList[n+1];
        for(int i=0;i<=n;i++)gr[i]=new ArrayList<>();
        
        for(int i=0;i<n-1;i++){
        int x=s.nextInt();
        int y=s.nextInt();
        gr[x].add(y);
        gr[y].add(x);
        
        
        }
        long count=0;
        for(int i=1;i<=n;i++){
        if(gr[i].size()>1){count+=((gr[i].size()*(gr[i].size()-1))/2);}
        
        }
        System.out.println(count);
    }
}
