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>
struct Node {
  uint16_t number = 0;
  std::vector<Node*> childs;
};
class Tree {
 public:
  Tree(std::vector<Node>&& adjLists) noexcept;
  Tree(Tree&& tree) noexcept;
  size_t get2Paths();

 private:
  std::vector<Node> m_nodes;
};
Tree readData(std::istream& stream);
int main() {
  Tree t = readData(std::cin);
  std::cout << t.get2Paths();
  return 0;
}
Tree readData(std::istream& stream) {
  uint16_t edgeCount;
  stream >> edgeCount;
  std::vector<Node> adjLists;
  adjLists.resize(edgeCount);
  for (uint16_t i = 0; i < edgeCount - 1; ++i) {
    uint16_t v1;
    uint16_t v2;
    stream >> v1 >> v2;
    --v1;
    --v2;
    adjLists[v1].number = v1;
    adjLists[v1].childs.push_back(&adjLists[v2]);
    adjLists[v2].number = v2;
    adjLists[v2].childs.push_back(&adjLists[v1]);
  }
  return Tree(std::move(adjLists));
}
Tree::Tree(std::vector<Node>&& adjLists) noexcept
    : m_nodes(std::move(adjLists)) {}
Tree::Tree(Tree&& tree) noexcept : m_nodes(std::move(tree.m_nodes)) {}
size_t Tree::get2Paths() {
  size_t pathsCount = 0;
  for (size_t i = 0; i < m_nodes.size(); ++i) {
    const Node& currentNode = m_nodes[i];
    for (size_t j = 0; j < currentNode.childs.size(); ++j) {
      const Node& child = *currentNode.childs[j];
      for (size_t k = 0; k < child.childs.size(); ++k) {
        const Node& grandChild = *child.childs[k];
        if (grandChild.number != currentNode.number) {
          ++pathsCount;
        }
      }
    }
  }
  return pathsCount / 2;
}
