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.*;
import java.io.*;

public class CF {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter pw = new PrintWriter(new OutputStreamWriter(System.out));

        HashSet<OrderedPair> set = new HashSet<>();
        ArrayList<ArrayList<Integer>> adj = new ArrayList<>();

        int n = Integer.parseInt(br.readLine());

        for (int i = 0; i < n; i++) {
            adj.add(new ArrayList<>());
        }

        for (int i = 0; i < n - 1; i++) {
            StringTokenizer st = new StringTokenizer(br.readLine());
            int a = Integer.parseInt(st.nextToken()) - 1;
            int b = Integer.parseInt(st.nextToken()) - 1;
            adj.get(a).add(b);
            adj.get(b).add(a);
        }

        for (int i = 0; i < n; i++) {
            for (Integer nbr1 : adj.get(i)) {
                for (Integer nbr2 : adj.get(nbr1)) {
                    if (i != nbr2) {
                        set.add(new OrderedPair(i, nbr2));
                    }
                }
            }
        }

        pw.println(set.size());
        pw.close();
    }

    static class OrderedPair {
        public int a, b;

        public OrderedPair(int x, int y) {
            if (x < y) {
                a = x;
                b = y;
            } else {
                a = y;
                b = x;
            }
        }

        public boolean equals(Object o) {
            if (o instanceof OrderedPair) {
                OrderedPair p = (OrderedPair) o;
                return p.a == a && p.b == b;
            }

            return false;
        }

        public int hashCode() {
            return new Integer(a).hashCode() * 31 + new Integer(b).hashCode();
        }

        @Override
        public String toString() {
            return "OrderedPair{" +
                    "a=" + (a + 1) +
                    ", b=" + (b + 1) +
                    '}';
        }
    }
}
