beecrowd | 1921
# Guilherme and His Kites

**Timelimit: 1**

By Gustavo Ribeiro, IFPB - Campina Grande Brazil

Guilherme loves kites, kites of different colors, forms and sizes. He realized that in order to kites become stable, and thus fly higher, they must have a taut string connecting all pairs of non-neighboors tips.

Despite being a very creative and clever child, Guilherme doesn’t know how to determine the number of strings necessary to make a kite of *n* sides stable. Could you help him?

The single line of the input contains an integer 3 ≤ **n** ≤ 10^{5}, the number of sides of the kite.

Print a single number, the number of strings that Guilherme needs to make a kite of **n** sides stable.

Input Samples | Output Samples |

4 |
2 |

10 |
35 |

11 |
44 |