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F1. Tree of Life (easy)

time limit per test

2 secondsmemory limit per test

256 megabytesinput

standard inputoutput

standard outputHeidi 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.

Codeforces (c) Copyright 2010-2021 Mike Mirzayanov

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