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.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;
import java.util.StringTokenizer;

public class Main{

	static PrintWriter writer = new PrintWriter(System.out,false);
	static boolean[] visited;
	static final int[] rowIncrement = {-1,0,0,1};   // possible moves in rows
	static final int[] colIncrement = {0,-1,1,0};
	static int count=0;
	static  ArrayList<Integer>[] al;
	static int dist[];
	static int nodes[],ans=0;
	public static void main(String[] args) throws IOException{
		int n,m,t,k1,k2;
		Scanner s=new Scanner(System.in);
		n=s.nextInt();
		visited=new boolean[n+1];
		Arrays.fill(visited, false);
		al=new ArrayList[n+1];
		for(int i=0;i<=n;i++)
			al[i]=new ArrayList();
		dist=new int[n+1];
		for(int i=0;i<n-1;i++){
			int a=s.nextInt();
			int b=s.nextInt();
			al[a].add(b);
			al[b].add(a);
		
		}

		dist[1]=0;
		dfs(1);
		System.out.println(ans);
	}
	private static void dfs(int i) {
		visited[i]=true;
		int count=0;
		for(int child:al[i]){
			if(!visited[child]){
				count++;
				dist[child]=dist[i]+1;
				if(dist[child]>=2)
					ans++;
				dfs(child);
			}
		}
		ans+=(count*(count-1))/2;
		//System.out.println(i+" " +ans);
		return ;
	}
}
