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>
long long int add(long long int a, long long int b) {
  return a + b - (a + b >= 1000000007) * 1000000007;
}
long long int sub(long long int a, long long int b) {
  return a - b + (a - b < 0) * 1000000007;
}
long long int mult(long long int a, long long int b) {
  return (1LL * a * b) % 1000000007;
}
inline long long int gcd(long long int a, long long int b) {
  long long int t;
  while (b) {
    a = a % b;
    t = a;
    a = b;
    b = t;
  }
  return a;
}
using namespace std;
bool visited[101] = {false};
vector<long long int> v1[101];
void DFS(long long int node) {
  if (visited[node] == true) {
    return;
  }
  visited[node] = true;
  for (long long int i = 0; i < v1[node].size(); i++) {
    DFS(v1[node][i]);
  }
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie();
  long long int n;
  cin >> n;
  long long int array[n + 1];
  for (long long int i = 0; i < n + 1; i++) {
    array[i] = 0LL;
  }
  for (long long int i = 1; i <= n - 1; i++) {
    long long int a, b;
    cin >> a >> b;
    array[a] += 1;
    array[b] += 1;
  }
  long long int ans = 0;
  for (long long int i = 1; i <= n; i++) {
    ans += (array[i] * (array[i] - 1)) / 2;
  }
  cout << ans;
  return 0;
}
