8.THE NECKLACE QUESTION

Credits: 300

PROBLEM DESCRIPTION:

Consider a necklace made of 2N-1 black and white beads, K of which are black. Necklace is called "beautiful" if it is possible to choose two black beads (not necessarily different) in such a way that one of two necklace parts strictly between them contains exactly N beads.

For example, if N=4 and K=3, necklace "WBWBWBW" is beautiful, and necklace "BBWWBWW" is not.

You need to find minimal K for which every necklace of 2N-1 beads is beatiful.

INPUT:

The first line of input contains odd integer number 2N-1 (5<=2N-1<=2^31-1).

OUTPUT:

Output minimal K for which every necklace of 2N-1 beads is beatiful.

SAMPLE INPUT:
Test #1
5
Test #2
7

SAMPLE OUTPUT:
Test #1
3
Test #2
4