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;
string toBin(long long int a) { return bitset<64>(a).to_string(); }
void printArr(int* a, int n) {
  for (int i = 0; i < n; i++) printf("%d ", a[i]);
  printf("\n");
}
string intToString(long long int a) {
  ostringstream temp;
  temp << a;
  return temp.str();
}
long long int pow(long long int base, long long int exponent) {
  long long int result = 1;
  while (exponent > 0) {
    if (exponent % 2 == 1) result *= base;
    exponent = exponent >> 1;
    base *= base;
  }
  return result;
}
long long int powerWithMod(long long int base, long long int exponent,
                           long long int modulus) {
  long long int result = 1;
  base %= modulus;
  while (exponent > 0) {
    if (exponent % 2 == 1) result = (result * base) % modulus;
    exponent = exponent >> 1;
    base = (base * base) % modulus;
  }
  return result;
}
bool isPrime(int n) {
  if (n == 2) return true;
  if (n % 2 == 0) return false;
  int limit = ceil(sqrt(n)) + 1;
  for (int d = 3; d <= limit; d += 2) {
    if (n % d == 0) return false;
  }
  return true;
}
int gc(string a, string b) {
  int i = 0, j = 0;
  for (i = 0; i < a.size(); i++) {
    if (a[i] == b[j] && j == b.size() - 1) return i;
    if (a[i] == b[j]) j++;
  }
  return -1;
}
class edge {
 public:
  int x;
  int y;
  edge(int a, int b) {
    x = a;
    y = b;
  }
  bool operator==(const edge& b) const {
    return (x == b.x || x == b.y || y == b.x || y == b.y);
  }
};
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  ;
  int n, ans = 0;
  cin >> n;
  vector<edge> a;
  for (int i = 1; i < n; i++) {
    int n1, n2;
    cin >> n1 >> n2;
    edge temp(n1, n2);
    a.push_back(temp);
  }
  for (int i = 0; i < n - 1; i++) {
    for (int j = i + 1; j < n - 1; j++) {
      if (a[i] == a[j]) ans++;
    }
  }
  cout << ans << "\n";
  return 0;
}
