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.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {

	private static List<Integer>[] edges;
	private static boolean visited[];
	private static int counter = 0;

	@SuppressWarnings("unchecked")
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		int n = scanner.nextInt();
		int from = 0, to;
		edges = (List<Integer>[]) new List<?>[n];
		visited = new boolean[n];
		for (int i = 0; i < n; i++)
			edges[i] = new ArrayList<>();
		for (int i = 0; i < n - 1; i++) {
			from = scanner.nextInt() - 1;
			to = scanner.nextInt() - 1;
			edges[from].add(to);
			edges[to].add(from);
		}
		getResult(from);
		System.out.println(counter / 2);
		scanner.close();
	}

	private static void getResult(int i) {
		visited[i] = true;
		for (int step1 : edges[i]) {
			for (int step2 : edges[step1])
				if (step2 != i)
					counter++;
			if (!visited[step1])
				getResult(step1);
		}
	}

}
