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.Scanner;
public class Saurav {
    public static void main(String[] arg) {
           Scanner sc = new Scanner(System.in);
           int n=sc.nextInt();
           int count=0;
           int a[][] = new int[10000][2];
           for(int i=0;i<n-1;i++)
           {
               for(int j=0;j<2;j++)
               {
                   a[i][j]= sc.nextInt();
               }
           }
           for(int i=0;i<n-2;i++)
           {
               for(int j=i+1;j<n-1;j++)
               {
                   if(a[i][0]==a[j][0] || a[i][1]==a[j][0] || a[i][1]==a[j][1] || a[i][0]==a[j][1])
                   {
                       count++;
                   }
               }
           }
           System.out.println(count);
    }
}