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 F1690 {
	public static void main(String[] args) {
		Scanner scan = new Scanner (System.in);
		int num = scan.nextInt();
		HashMap<Integer, Integer> hash = new HashMap<Integer, Integer>();
		int total = 0;
		for (int i = 0; i < (num-1)*2; i++) {
			int current = scan.nextInt();
			
			if (hash.containsKey(current)) {
				hash.put(current, hash.get(current) + 1);
			} else {
				hash.put(current, 1);
			}
			
		}
		
		for (Integer x: hash.keySet()) {
			int times = hash.get(x);
			total += times*(times-1)/2;
		}
		
		System.out.println(total);
		
	}
}
