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.
/*-
 * Codeforces problem :
 * http://codeforces.com/problemset/problem/690/F1
 *
 * Print one integer – the number of lifelines in the tree.
 * 
 */

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

/**
 * @author Karthik Venkataraman
 * @email kafy83@gmail.com
 */
public class TreeOfLife {

    private void compute() {
        InputReader sc = new InputReader(System.in);
        int n = sc.nextInt();
        int[] degree = new int[n];
        for (int i = 0; i < (2 * n - 2); i++) {
            degree[sc.nextInt() - 1]++;
        }
        long ans = 0;
        for (int i = 0; i < n; i++) {
            ans += (degree[i] * (degree[i] - 1)) >> 1;
        }
        System.out.print(ans);
    }

    class InputReader {

        private static final int INPUT_KB = 1024;
        private BufferedReader reader;
        private StringTokenizer tokenizer;

        InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), INPUT_KB);
        }

        String readNext() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException ex) {
                    throw new IllegalArgumentException(ex);
                }
            }
            return tokenizer.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(readNext());
        }
    }

    public static void main(String... args) {
        TreeOfLife tl = new TreeOfLife();
        tl.compute();
    }
}