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!

The first line of the input contains a single integer n — the number of vertices in the tree (1 \le n \le 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 \le a \lt b \le n). It is guaranteed that the input represents a tree.

Print one integer — the number of lifelines in the tree.

In the second sample, there are four lifelines: paths between vertices 1 and 3, 2 and 4, 2 and 5, and 4 and 5.