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.*;

/**
 * 9/17/16 11:01 AM.
 */
public class TreeOfLife {
    static class Pair {
        int a,b;
        Pair(int a, int b) {
            this.a = a;
            this.b = b;
        }

        @Override
        public boolean equals(Object obj) {
            boolean result = false;
            Pair p = (Pair)obj;
            if(this.a == p.a) {
                if(this.b == p.b) {
                    result = true;
                }
            } else if(this.a == p.b) {
                if(this.b == p.a) {
                    result = true;
                }
            }

            return result;
        }

        @Override
        public String toString() {
            return "["+ a +  "," + b+ "]";
        }
    }

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        Set<Pair> resultSet = new HashSet<>();
        ArrayList<Integer>[] tree = (ArrayList<Integer>[])new ArrayList[n+1];

        for(int i = 0; i < (n - 1); i++) {
            int v0 = scan.nextInt();
            int v1 = scan.nextInt();
            if(tree[v0] == null)
                tree[v0] = new ArrayList<>();
            if(tree[v1] == null)
                tree[v1] = new ArrayList<>();
            tree[v0].add(v1);
            tree[v1].add(v0);
        }

        for(int i = 1; i < tree.length; i++) {
            ArrayList<Integer> a = tree[i];
            for(int v : a) {
                ArrayList<Integer> b = tree[v];
                for(int e : b) {
                    if(e != i) {
                        Pair r = new Pair(i, e);
                        resultSet.add(r);
                    }
                }
            }
        }

        System.out.println(resultSet.size()/2);
    }

}