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;
const int MaxN = 2e4;
int n, all;
int pre[MaxN + 5], last[MaxN + 5], other[MaxN + 5];
long long f[MaxN + 5];
long long ans;
void Build(int x, int y) {
  pre[++all] = last[x];
  last[x] = all;
  other[all] = y;
}
void Init() {
  all = -1;
  memset(last, -1, sizeof(last));
  for (int i = 1; i <= n - 1; i++) {
    int u, v;
    scanf("%d%d", &u, &v);
    Build(u, v);
    Build(v, u);
  }
  ans = 0;
}
void Dfs(int x, int fa) {
  int ed = last[x], dr;
  f[x] = 0;
  while (ed != -1) {
    dr = other[ed];
    if (dr != fa) {
      Dfs(dr, x);
      ans += f[dr];
      f[x]++;
    }
    ed = pre[ed];
  }
  ans += f[x] * (f[x] - 1) / 2;
}
int main() {
  while (~scanf("%d", &n)) {
    Init();
    Dfs(1, 0);
    printf("%I64d\n", ans);
  }
}
