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.*;
import java.util.*;
public class TreeofLife
{
	public static void main(String args[])throws IOException
	{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(br.readLine());
		int n = Integer.parseInt(st.nextToken());
		//int m = Integer.parseInt(st.nextToken());
		
		
			Graph nerve = new Graph(n);
			for(int i=0;i<n-1;i++)
			{	
				st = new StringTokenizer(br.readLine());
				int v = Integer.parseInt(st.nextToken());
				int w = Integer.parseInt(st.nextToken());
				nerve.addEdge(v-1,w-1);
			}
			
			System.out.println(nerve.lifepath());
		
	}
}
class Graph
{
	ArrayList<Integer> adj[];
	public Graph(int v)
	{
		adj = (ArrayList<Integer>[])new ArrayList[v];
		for(int i=0;i<v;i++)
			adj[i] = new ArrayList<Integer>();

	}
	public void addEdge(int v, int w)
	{
		adj[w].add(v);
		adj[v].add(w);
	}
	public int V()
	{
		return adj.length;
	}
	public int lifepath()
	{
		int count=0;
		for(int i=0;i<adj.length;i++)
		{
			count+=((adj[i].size()-1)*adj[i].size())/2;
		}
		return count;
	}
}
