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.io.*;
public class JavaApplication4{
    public static void main(String[] args) throws IOException
    {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(br.readLine());
        int ab[][] = new int[n - 1][2];
        for(int x = 0; x < n - 1; x++)
        {
            String input = br.readLine();
            String temp = "";
            for(int y = 0 ; y < input.length(); y++)
            {
                if(input.charAt(y) == ' ')
                {
                    ab[x][0] = Integer.parseInt(temp);
                    y++;
                    temp = "";
                }
                temp = temp + input.charAt(y);
            }
            ab[x][1] = Integer.parseInt(temp);
        }
        
        int count = 0;
        for(int x = 0; x < n - 2; x++)
        {
            for(int y = x + 1; y < n - 1; y++)
            {
                if((ab[x][0] == ab[y][0]) && (ab[x][1] != ab[y][1])) count++;
                if((ab[x][1] == ab[y][0]) && (ab[x][0] != ab[y][1]))count++;
                if((ab[x][0] == ab[y][1]) && (ab[x][1] != ab[y][0]))count++;
                if((ab[x][1] == ab[y][1]) && (ab[x][0] != ab[y][0]))count++;
            }
        }
        
        System.out.print(count);
    }
}
 
