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.
#include <bits/stdc++.h>
using namespace std;
long long n;
struct node {
  long long col;
  vector<long long> to;
  node() { col = 0; }
};
vector<node> g;
long long res = 0;
void dfs(long long u) {
  g[u].col = 1;
  res += g[u].to.size() * (g[u].to.size() - 1) / 2;
  for (long long i = 0; i < g[u].to.size(); i++) {
    long long v = g[u].to[i];
    if (g[v].col == 1) continue;
    dfs(v);
  }
}
int main() {
  cin >> n;
  g.resize(n + 1);
  for (long long i = 0; i < n - 1; i++) {
    long long a, b;
    cin >> a >> b;
    g[a].to.push_back(b);
    g[b].to.push_back(a);
  }
  dfs(1);
  cout << res;
  return 0;
}
