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.Scanner;

public class LifeTree {

	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		// System.out.print("Enter count: ");
		String input = scanner.next();
		
		int n = Integer.parseInt(input);
		
		// System.out.println("Count: " + n);
		
		int[] degree = new int[n];
		
		
		int vertex;
		for (int i = 0; i < n - 1; i++) {
			// System.out.print("Enter next line: ");
			for (int j = 0; j < 2; j++) {
				vertex =  Integer.parseInt( scanner.next() );
				degree[vertex - 1]++;
			}
		}
		
		// System.out.print("degrees: ");
		for (int i = 0; i < n; i++) {
			// System.out.print( (i + 1) + " => " + degree[i] + "; " );
		}
		
		System.out.println(getLifeLinesCount(degree));
		
	}
	
	private static int getLifeLinesCount(int[] degree) {
		int count = 0;
		for (int i = 0; i < degree.length; i++) {
			count += degree[i] * degree[i] - degree[i];
		}
		return count / 2;
	}

}
