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.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;

public class MainFeasy {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        String line1 = br.readLine();
        int N = Integer.parseInt(line1);

        Vertex[] ver = new Vertex[N];
        for(int i = 0; i<N; i++) ver[i] = new Vertex();

        for(int i = 1; i<N; i++){
            String line = br.readLine();
            String[] split = line.split(" ");
            int a = Integer.parseInt(split[0]);
            int b = Integer.parseInt(split[1]);
            a--;
            b--;
            ver[a].paths.add(b);
            ver[b].paths.add(a);
        }

        int total = 0;
        for(int i = 0; i<N; i++){
            ver[i].visited = true;
            for(int neigh : ver[i].paths){
                for(int neigh2 : ver[neigh].paths){
                    if(!ver[neigh2].visited){
                        //System.out.println((i+1) + " " + (neigh + 1) + " " + (neigh2 + 1));
                        total++;
                    }
                }
            }
        }
        System.out.println(total);
    }
}

class Vertex{
    ArrayList<Integer> paths;
    boolean visited;
    Vertex(){
        paths = new ArrayList<>();
        visited = false;
    }
}