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 TreeLife
{
	public static void main(String args[])
	{
		int v;
		int x[],y[];
		int count=0;
		Scanner in=new Scanner(System.in);
		v=in.nextInt();
		x=new int[v-1];
		y=new int[v-1];
		for(int i=0;i<v-1;i++)
		{
			x[i]=in.nextInt();
			y[i]=in.nextInt();
		}
		for(int i=0;i<v-1;i++)
		{
			for(int j=0;j<v-1;j++)
			{
					if(i!=j &&(x[i]==x[j] || y[i]==y[j] || y[i]==x[j] || x[i]==y[j]))
					{
						count++;
					}
			}
		}
		System.out.println(count/2);
		
	}
}